DRAKE'S 

ELECTRICAL 
DICTIONARY 


LOWE 


Drake's 
Electrical   Dictionary 


A  Compendium  of  Words,  Terms 
and  Phrases  Used  in  the  Electrical 
Trades  and  Electrical  Engineering 


By 
PAUL  E.  LOWE,  M.  E. 

Assisted   by    a  Corps    of   Electrical    Engineers    and 
Writers  on  Electrical  Subjects 


CHICAGO 
FREDERICK  J.  DRAKE  &  CO. 

Publishers 


UG 


Copyright  1915 

By  Frederick  J.   Drake  &  Co., 
Chicago 


••  —     "    -*- 


•• 

.' 

PREFACE 

The  prime  object  of  DRAKE'S  ELECTRICAL  DICTION- 
ARY is  to  bring  together  for  convenient  reference  the 
words,  terms  and  phrases  used  in  the  electrical  world. 

The  tremendous  growth  in  interest  in  the  electrical 
arts,  trades  and  sciences  makes  some  method  of  quick 
reference  a  practical  necessity.  It  is  hoped  that  the 
manner  of  presentation  "followed  in  this  book  will 
prove  to  be  most  advantageous. 

Many  practical  difficulties  arise  in  arranging  all 
words  and  phrases  alphabetically.  The  single  words 
fall  into  place  naturally  enough,  but  in  placing  the 
phrases  the  question  of  which  word  of  the  phrase  is 
to  have  the  alphabetic  position  is  important.  The  gen- 
eral plan  of  using  the  first  words  of  all  phrases  has 
been  adopted.  Thus  an  endless  number  of  annoying 
cross  references  have  been  avoided. 

In  any  field  of  science  in  which  growth  has  been  and 
continues  to  be  so  rapid,  it  is  only  natural  that  words 
and  terms  are  not  absolutely  fixed.  Without  making 
the  work  too  voluminous,  however,  we  have  endeavored 
to  include  all  those  words  and  terms  in  common  use, 
though  many  are  used  interchangeably. 

Every  effort  has  been  made  to  produce  a  book  of  the 
greatest  practical  utility  to  every  one  who  has  any  in- 
terest in  the  subject  of  electricity. 


3O2QPO 


ELECTRICAL  DICTIONARY. 


A 

A.  C. — An  abbreviation  expressing  an  alternating 
current. 

Absolute. — Complete  by  itself.  Independent  of  any 
other  element. 

Absolute  Unit  of  Current. — A  current  possessing  a  de- 
gree of  strength,  and  which  when  transmitted 
through  a  wire  which  has  been  curved  in  the  shape 
of  an  arc  of  a  circle  of  one  centimetre  radius,  will 
act  on  a  one-unit  power  magnetic  pole,  stationed 
at  the  center  of  the  arc,  with  a  force  equal  to  one 
degree.  A  10  amperes  current. 

Absolute  Unit  of  Electromotive  Force. — The  electro- 
motive force  unit  C.  G.  S. 

Absolute  Vacuum. — A  void  produced  by  the  exhaustion 
of  all  residual  gases. 

Absorption. — The  act  of  one  form  of  material  substance 
sucking  or  drawing  in  some  other  form  of  matter. 
The  sucking  in  of  water  by  a  sponge  or  the  draw: 
ing  in  of  vapors,  gases,  light,  electricity,  energy  or 
heat  by  any  other  material  substance. 

Absorption  Power. — A  property  peculiar  to  certain  ma- 
terials by  which  they  draw  in  gases  through  their 
pores  and  condense  them. 

Acceleration. — The  increase  or  decrease  of  motion  or 
action.  The  time  period  of  mutation  in  velocity. 
1 


2  ;  \    ELECTRICAL  DICTIONARY 

Accumulated  Siectricity.-r-Electricity  confined  or  stored 
as  in  a  condenser. 

Accumulating  Electricity. — Confining  or  placing  elec- 
tricity in  storage. 

Accumulation  of  Electricity. — The  gathering  of  elec- 
tric charges  in  condensers  or  Leyden  jars.  An 
electric  charge  augmented  by  aid  of  a  device 
term  an  accumulator.  A  charge  produced  by  the 
use  of  an  influence  machine.  The  gathering  of 
electricity  by  storage  batteries  or  accumulators. 

Accumulator. — A  term  sometimes  used  to  designate  a 
current  accumulator.  A  condenser,  a  Leyden  jar, 
a  storage  battery. 

Acetometer  or  Acidometer. — A  graduated  hydrometer 
used  to  ascertain  the  strength  of  acetic  acid  or 
vinegar. 

Achromatic  Lens. — A  lens  producing  images  without 
false  coloring. 

Acidometer. — (See  Acetometer.) 

Acoustic. — Pertaining  to  the  sense  of  hearing,or  sound. 

Acoustic  Absorption. — The  absorbing  by  one  vibrating 

object  or  mass  of  the  sound-wave  energy  created 

by  another  vibrating  object  or  mass. 

Acoustic  Interference. — Mutual  influence  of  sound- 
waves upon  each  other. 

Acoustic  Synchronizer. — A  contrivance  employed  to 
mark  the  synchronism  of  two  alternating  currents. 
An  acoustic  apparatus  in  which  at  synchronism 
silence  is  effected. 

Actinic. — Pertaining  to  chemical  changes  produced  by 


ELECTRICAL  DICTIONARY  3 

the  sun's  rays,  or  radiators  from  other  sources  of 
energy. 

Actinic  Photometer. — A  photometer  which  determines 
the  intensity  of  light  by  the  quantity  of  decompo- 
sition which  is  chemically  obtained  in  it. 

Actinic  Ray. — Any  form  of  radiating  energy  having 
the  property  to  induce  chemical  action. 

Actinometer. — An  apparatus  for  determining  the  de- 
gree of  energy  in  the  chemical  effects  of  light. 

Active  Coil  or  Conductor. — A  coil  or  conductor  con- 
veying a  current  of  electricity. 

Active  Current. — The  active  constituent  of  a  current 
in  an  alternating  current  circuit,  in  contradistinc- 
tion from  the  wattless  component  of  current. 

Active  Electromotive  Force. — That  constituent  of  the 
impressed  electromotive  force  in  an  alternating 
current  which  is  employed  to  surmount  the  ohmic 
resistance,  in  contradistinction  from  the  compon- 
ent employed  to  overcome  the  induced  C.  E.  M.  F. 

Active  Material  Storage  Cell. — The  matter  which  de- 
composes while  charging  or  discharging  in  a 
storage  or  secondary  cell  and  which  performs  the 
function  of  storing  electricity. 

Active  Plate  of  Voltaic  Cell. — A  term  applied  to  the 
zinc  and  other  metallic  plates  used  in  voltaic  or 
primary  cells,  and  which  dissolve  in  the  process  of 
active  operation. 

Active  Polar  Surface  of  Magnet.— The  surface  of  a  mag- 
net which  emits  or  absorbs  the  useful  flux. 

Active  Wire. —  The  section  of  wire  on  the  armature  of 
a  dynamo  which  goes  through  the  inducing  mag- 


4  ELECTRICAL  DICTIONARY 

netic    flux,    in    contradistinction    from    the    "idle 

wire,"  or  the  remaining  wire  which  does  not  pass 

through  the  flux. 
Activity. — Power.    Rate  of  performance.    Performance 

per  second  in  invariable  operation. 
Actual    Efficiency. — Efficiency    answering    commercial 

purposes. 
Acute  Angle. — An  angle  less  than  90  degrees,  or  less 

than  a  right  angle. 

Adapter. — A  threaded  projection  attached  to  an  incan- 
descent electric  lamp  by  means  of  which  the  lamp 
can  be  screwed  to  gas  fixtures  in  the  place  of  gas 
burner.  A  device  enabling  a  lamp  of  any  one  manu- 
facture to  be  fitted  into  the  socket  of  the  lamp  of 
every  other  manufacture.  An  apparatus  contrived 
to  modify  the  continuous  electric  current  used  in 
incandescent  service,  in  order  that  the  mild  contin- 
uous currents  employed  in  electro-therapeutics  may 
be  obtained. 

Adhesion. — An  attraction  existing  between  heteroge- 
neous molecules  in  contradistinction  from  cohesion 
or  the  mutual  attraction  of  homogeneous  mole- 
cules. 

Adhesion,  Electric. — The  adhesion  of  two  surfaces  re- 
sulting from  the  attraction  of  dissimilar  electro- 
static charges. 

Adhesion,  Magnetic. — The  adhesion  of  surfaces  result- 
ing from  magnetic  flux. 

Adhesive  Tape. — A  tape  rendered  adhesive  by  the  ap- 
plication of  an  adhesive  insulating  material,  and 
used  to  protect  bare  conductors  at  joints  and  other 
exposed  points. 


ELECTRICAL  DICTIONARY  5 

Adiabatic  Expansion. — The  expansion  of  a  gas  in  a 
chamber  whose  walls  receive  no  heat  from  the  gas 
nor  convey  any  to  it  differing  tlius  from  isothermal 
expansion. 

Adjustable  Condenser. — A  condenser,  the  capacity  of 
which  is  susceptible  of  variation  within  prescribed 
limits. 

Adjustable  Resistance. — A  resistance,  the  degree  of 
which  is  easily  varied  within  prescribed  limits. 

Adjustable  Rheostat. — A  resistance  readily  adjusted. 

Adjustable  Vacuum  Tube. — A  vacuum  tube  designed 
for  X-ray  examinations;  the  vacuum  in  which  is 
diminishable  by  heat  acting  upon  a  vaporizable 
substance. 

Adjuster  for  Lamp  Pendant. — A  device  of  any  descrip- 
tion suitable  for  making  adjustments  or  changes 
in  altitude  or  position  of  pendant  lamps. 

Adjusting  Cleat. — A  cleat  susceptible  to  adjustment 
with  reference  to  altitude  or  alignment. 

Adjustment. — Any  change  in  an  apparatus  which  will 
insure  correct  performance  of  its  office. 

Adjustment  of  Relay. — That  regulation  of  a  receiving 
relay  which  insures  ready  response  to  signals  for- 
warded over  the  line. 

Aerial  Circuit. — The  section  of  a  circuit  composed  of 
aerial  lines  or  conductors.  An  elevated  circuit  of 
wire. 

Aerial  Conductor. — A  conductor  erected  overhead. 
Aerial  Line. — A  line  erected  overhead. 
Aerodynamics. — The  science  which  treats  of  the  motion 
of  air  and  its  mechanical  effect  when  in  motion. 


6  ELECTRICAL  DICTIONARY 

Aero- Ferric  Inductance. — The  inductance  inherent  in  a 
coil,  the  magnetic  circuit  of  which  is  composed  in 
parts  of  air  and  iron. 

After  Glow. — A  fluorescent  glow  visible  in  an  exhausted 
container  of  glass  after  removal  from  electrostatic 
influence. 

Age-Coating  of  Electric  Incandescent  Lamp  Chamber. — 
A  black  coating  from  carbon  and  other  like  sub- 
stances deposited  in  the  chamber  of  an  incandescent 
lamp  while  in  active  service. 

Aging  of  Alcohol,  Electric. — The  artificial  aging  of 
alcohol  by  subjecting  it  to  the  action  of  ozone  gen- 
erated by  electricity. 

Aging  of  Electric  Incandescent  Lamp. — A  diminishing 
by  degrees  of  the  capacity  of  an  electric  incandes- 
cent lamp  resulting  from  either  age-coating  or  im- 
pairment of  the  filament. 

Aging  of  Transformer. — A  diminution  in  the  capacity 
of  a  transformer  due  to  its  core  becoming  old. 
Transformer  fatigue. 

Agone. — A  line  on  the  earth's  surface  on  which  the 
magnetic  needle  points  to  the  true  north,  the  mag- 
netic meridian  coinciding  with  the  geographical. 

Air  Blast  for  Commutator. — A  blast  of  air  played  upon 
the  surface  of  the  commutator  of  an  electric  dyna- 
mo to  obviate  damaging  flashes. 

Air  Blast  Transformer. — A  transformer  which  is  kept 
cool  by  the  application  of  an  air  jet. 

Air  Churning. — The  motion  of  the  air  contiguous  to  the 
armature  of  a  dynamo  or  motor  while  rotating,  oc- 
casioning a  loss  of  energy. 

Air  Core  Solenoid. — A  solenoid  whose  sole  core  is  air. 


ELECTRICAL  DICTIONARY  7 

Air  Gap.— Any  gap  or  aperture  in  a  magnetic  circuit 

which  contains  air  only. 
Air  Gap  Commutator. — The  air  space  between  the  parts 

of  contaction  in  an  air-insulated  commutator. 

, 

Air  Insulation. — Insulation  procured  by  the  action  of 
air. 

Air  Pump. — A  contrivance  employed  to  withdraw  the 
air  and  other  gases  from  a  vessel. 

Air  Resistance  of  Dynamo. — The  mechanical  resistance 
opposed  by  the  surrounding  air  to  the  rotary  mo- 
tion of  a  dynamo. 

Air  Space. — The  space. existing  between  the  polar  sur- 
face within  wiiic'h  an  armature  rotates,  and  the 
surface  of  the  armature  itself.  The  space  in  a 
comb  lightning  arrester  between  the  opposing  sur- 
faces. 

Alarm  Electric. — Any  electric  contrivance  which,  work- 
ing automatically,  directs  attention,  by  the  open- 
ing and  closing  of  a  circuit,  to  certain  occurrences, 
i.  e. :  the  movement  of  doors  or  windows,  the  reach- 
ing of  certain  prescribed  limits  in  the  rise  and  fall 
of  temperature,  footsteps  in  certain  places,  etc.  A 
device  used  to  summon  a  person  to  a  telephone  or 
a  telegraphic  instrument. 

"Alive." — A  term  applied  to  live  circuits  or  wires. 
Active  circuits  or  wires. 

All-Night  Arc  Lamp. — An  arc  lamp  with  a  double 
carbon. 

Allotropic  State. — The  property  of  substances  of  exist- 
ing in  two  or  more  conditions  which  are  distinct 
in  their  physical  relation,  but  without  change  in 


8  ELECTRICAL  DICTIONARY 

their  chemical  composition,  i.  e. :  the  various  modi- 
fications of  carbon. 

Alloy. — Any  compound  of  two  or  more  metals,  as  of 
copper  and  zinc  to  form  brass. 

Alternate  Currents. — Currents  which  alternate. 
Alternating. — Having  a  periodical  change  in  direction. 
Alternating  Arc. — An  arc  with  alternating  current.    An 

arc  which  receives  its  supply  from  an  alternating 

current  circuit. 

Alternating  Continuous-Current  Commutating  Machine. 

A  secondary  generator,  which  by  aid  of  a  commu- 
tator, is  employed  to  change  an  alternating  to  a 
continuous  current. 

Alternating-Current  Dynamo-Electric  Machine. — A  dy- 
namo-electric machine  which  produces  in  its  ex- 
ternal circuit  currents  that  alternate. 

Alternating-Current  Electric  Mo-tor. — A  motor  impelled 
by  currents  that  alternate. 

Alternating-Current  Electro-Magnet.— An  electro-mag- 
net, the  coils  of  which  are  traversed  by  alternating 
currents,  and  whilst  continually  reversing  in  mag- 
netism, yet  maintains  a  constant  attraction  for  the 
armature. 

Alternating-Current  Phase-Meter.— -An  apparatus  em- 
ployed to  determine  the  phase  difference  between 
two  alternating  currents. 

Alternating-Current  Power. — Electric  power  furnished 
with  alternating  currents.  The  result  of  the  effi- 
cient alternating  current  force,  the  energy  of  pres- 
sure under  which  the  current  is  obtained,  and  the 
power  factor. 


ELECTRICAL  DICTIONARY  9 

Alternating-Current  Pressure  Indicator. — An  alternat- 
ing current  volt-meter. 

Alternating-Current  Regulator. — A  contrivance  em- 
ployed to  regulate  the  pressure  of  an  alternating 
current  generator,  with  a  view  to  maintaining  con- 
stancy. A  regulator  employed  to  govern  the 
strength  of  an  alternating  current. 

Alternating-Current  Transmission. — Transmission  of 
power  by  the  use  of  alternating  currents. 

Alternating  Currents. — Currents  flowing  in  opposite  di- 
rections and  alternating.  Currents  which  reverse 
their  direction  periodically. 

Alternation. — A  change  of  direction.  A  change  of  di- 
rection by  an  electro-motive  current.  One  vibration 
instead  of  an  entire  cycle  or  a  double  vibration. 

Amalgam. — A  compound  of  mercury  or  quick  silver 
with  any  other  metal. 

Amalgam,  Electric. — A  substance  used  to  cover  the  rub- 
bers of  frictional  electric  machines. 

Amalgamate. — To  convert  into  an  amalgam. 

Amalgamation  of  Zinc. — A  salt  of  mercury  solution 
used  in  amalgamating  the  zincs  of  voltaic  batteries. 

Amber. — A  yellowish,  resinous  substance  found  as  a 
fossil  in  alluvial  soils. 

American  Morse  Code. — The  telegraphic  code  invented 
by  Morse,  and  used  almost  exclusively  in  the 
United  States. 

American  Wire  Gauge. — The  name  by  which  the  Brown 
&  Sharpe  wire  gauge  is  known,  in  which  the  diam- 
eter of  the  largest  wire,  No.  0000,  is  0.46  inches, 
and  wire  No.  36,  0.005  inches,  and  all  other  diam- 
eters progress  geometrically. 


10  ELECTRICAL  DICTIONARY 

Ammeter. — Any  sort  of  galvanometer  which  can  meas- 
ure the  strength  of  currents  in  amperes  directly. 

Amorphous. — Devoid  of  definite  crystalline  form. 

Amperage. — The  num'ber  of  amperes  which  pass 
through  a  circuit  in  a  stated  time. 

Ampere. — The  accepted  unit  of  electric  current.  A 
flow  of  electricity  at  a  rate  which  transmits  one 
coulomb  per  second.  The  current  which  could  pass 
through  a  circuit  that  offered  a  resistance  of  one 
ohm  under  a  one-volt  electro-motive  force. 

Ampere-Hour. — A  unit  of  quantity  equal  to  the  amount 
of  electricity  transmitted  by  one  ampere  flowing 
during  one  hour. 

Ampere-Hour  Efficiency  of  Storage  Battery. — The  rate 
between  the  ampere-hours  consumed  from  and 
those  supplied  to  a  storage  battery  in  a  cycle  of 
charge  and  discharge. 

Ampere-Turn. — A  unit  of  magneto-motive  force  equal 
to  the  force  resulting  from  the  effect  of  one  am- 
pere passing  around  a  single  turn  of  wire. 

Ampere's  Rule  for  Deflection  of  Needle. — The  deflection 
of  the  north-seeking  pole  of  a  magnetic  needle  by  a 
current  at  the  left  of  an  object  assumed  to  be 
facing  the  needle  from  a  point  in  the  current. 

Amyloid. — A  material  used  itf  making  incandescent 
lamp  filaments  and  which  is  obtained  by  subjecting 
cellulose  to  the  action  of  sulphuric  acid.  A  cellu- 
lose parchment. 

Amyloid  Filament. — A  filament  made  of  amyloid. 

Analysis. — The  resolution  of  any  object  into  its  con- 
stituent or  original  elements  in  order  to  determine 
its  composition. 


ELECTRICAL  DICTIONARY  11 

Analysis  Electric. — The  resolution  of  a  compound  sub- 
stance into  elementary  constituents  by  electrical 
process  in  order  to  determine  its  composition. 

Anchored  Filament. — A  means  providing  for  the  sup- 
port of  an  incandescent  lamp  filament  at  its  center 
in  order  to  obviate  injury  by  too  violent  vibration. 

Anemometer. — An  instrument  for  measuring  the  force 
and  velocity  of  the  wind. 

Anemometer,  Electric. — An  instrument  for  recording 
"the  force  and  direction  of  the  wind  by  use  of  elec- 
tricity. 

Aneroid  Barometer. — An  instrument  for  measuring  at- 
mospheric pressure,  the  action  of  which,  depends 
upon  the  varying  pressure  of  the  atmosphere  upon 
the  elastic  top  of  a  metallic  box  from  which  the  air 
has  been  exhausted. 

Angle. — The  difference  in  direction  of  two  lines  in  the 
same  plane  that  meet  in  a  point  or  that  would  meet 
if  sufficiently  extended. 

Angle  of  Lead. — The  forward  angular  departure  from 
the  established  position,  which  the  collecting 
brushes  must  be  required  to  undergo  on  commu- 
tator of  a  continuous  current  generator,  to  the  end, 
that  quiet  commutation  may  be  obtained. 

Animal  Magnetism. — A  term  applied  to  the  phenomena 
of  hypnotism,  mesmerism,  etc. 

Annealing. — A  process  for  softening  metals  by  first 
heating  and  then  permitting  them  to  cool  gradu- 
ally. 

Annealing,  Electric. — An  annealing  process  by  means  of 
electric  heat  instead  of  heat  produced  in  the  or- 
dinary way. 


12  ELECTRICAL  DICTIONARY 

Annunciator  Board. — A  board  equipped  with  annunci- 
ator drops. 

Annunciator  Drop. — A  signal,  which  when  it  drops,  an- 
nounces the  closing  or  opening  of  the  circuit  of 
an  electro-magnet  connected  with  the  annunciator. 

Annunciator  Wire. — Insulated  wire  of  a  kind  adaptable 
to  annunciator  circuits. 

Anode. — The  positive  pole  of  an  electric  battery,  or 
preferably  the  path  by  which  the  current  passes 
out  and  enters  the  electrolyte  on  its  way  to  the 
other  pole;  opposed  to  the  cathode. 

Anomalous. — Deviation  from  a  general  rule.  Abnor- 
mal. Irregular. 

Anomalous  Helix. — A  helix  wound  in  such  manner  as 
to  create  an  anomalous  magnet. 

Anomalous  Magnet. — A  magnet  having  more  than  two 
free  poles. 

Anomalous  Magnetization. — The  magnetization  which 
the  vibrating  discharge  of  a  Ley  den  jar  or  conden- 
ser produces.  Magnetization  from  which  more  than 
two  free  poles  in  a  magnet  result. 

Answering  Jacks. — The  jacks  in  a  panel  of  a  telephone 
switchboard  which  are  connected  with  those  sub- 
scribers whose  calling  drops  are  in  the  same  panel, 
in  order  that  each  call  may  be  promptly  answered 
at  a  contiguous  jack. 

Anti-Induction  Telephone  Cable. — A  telephone  cable 
which,  by  reason  of  a  particular  arrangement  of 
its  conductors,  neutralizes  the  effects  of  induction 
caused  by  neighboring  circuits.  A  telephone  cable 
which  is  protected  from  the  effects  of  electrostatic 


ELECTRICAL  DICTIONARY  13 

induction  from  adjacent  circuits  by  a  covering  of 
metal  which  is  grounded  at  fitting  intervals. 

Antimonious  Lead. — A  compound  of  lead  and  antimony, 
which,  being  proof  against  the  action  of  a  charging 
current,  is  used  for  the  grid  of  a  storage  battery. 

Aperiodic. — Not  possessing  periodicity.  Attaining  re- 
pose without  vibrations. 

Aperiodic  Galvanometer. — A  galvanometer  the  needle 
of  which  attains  repose  without  vibrations.  A 
dead-beat  galvanometer. 

Apparent  Electro-motive  Force. — The  apparent  acting 
of  the  E.  M.  F.  in  a  circuit,  as  measured  by  the 
drop  of  pressure  occasioned  by  the  resistance  of 
the  circuit,  and  the  force  of  current  flowing 
through  it. 

Aqueous  Solution. — Substances  dissolved  in  water. 

Arc. — A  segment  of  a  circle.    A  voltaic  arc. 

Arc. — To  discharge  in  voltaic  arc  form. 

Arc-Circuit  Cut-Out. — A  cut-out  used  in  a  series  arc- 
light  circuit  to  obviate  the  breaking  of  the  whole 
circuit  in  the  event  of  the  extinguishment  of  any 
one  lamp. 

Arc-Lamp,  Electric. — An  electric  lamp  which  derives 
its  light  from  the  voltaic  arc.  An  incandescent 
lamp  used  in  observatories  to  light  the  circles  of 
telescopes  and  other  instruments. 

Arc-Lamp  Hanger. — A  board  from  which  an  arc-lamp 
hangs  and  is  equipped  with  electric  connections. 

Arc-Lamp  Spark-Arrester. — A  gauze  protector  enclos- 
ing the  arc,  to  guard  against  fire  where  arc  lamps 
are  used  in  dangerous  proximity  to  combustible  ma- 
terfals,  as  in  store  windows. 


14  ELECTRICAL  DICTIONARY 

Arc-Light. — The  carbon  voltaic  arc  light. 

Arc-Light    Generator. — A    dynamo    electric    machine 
which  supplies  arc-light  circuits  with  the  current. 

Arc-Light  Projector. — An  arc  lamp  provided  with  a  re- 
flector for  obtaining  a  beam  of  approximately  par- 
allel rays  of  light. 

Arc  Plug-Switchboard. — A  -switchboard  equipped  with 
spring-jacks  contacts  and  which  connect -with  the 
terminals  of  various  circuits  and  plug  switches  con- 
nected to  dynamo  terminals,  so  that  the  connection 
between  any  dynamo  and  any  circuit  can  be  made. 
Several  circuits  connected  to  the  one  dynamo,  or 
several  dynamos  located  in  the  same  circuit. 

Arc  Standard  of  Light. — A  standard  obtained  by 
means  of  the  photometer,  determining  the  inten- 
sity of  the  light  which  is  given  out  by  a  certain 
predetermined  crater  area  of  the  positive  carbon 
of  a  carbon  arc. 

Aerometer. — An  instrument  for  measuring  the  speci- 
fic gravity  of  fluids. 

Areometry. — The  act  of  measuring  the  specific  gravity 
of  fluids. 

Armature. — A  body  of  iron  or  other  material  suscep- 
tible to  magnetization  and  which  is  placed  on  or 
contiguous  to  the  poles  of  a  magnet.  That  part  of 
a  dynamo  electric  machine  termed:  the  armature. 

Armature  Bars. — Heavy  conductors  used  for  armature 
windings.  Heavy  copper  bars  used  instead  of  the 
usual  wire  windings  on  large  drum  armatures,  and 
in  form  of  rectangular  cross-section  strips. 

Armature  Binding  Wires. — Wire  coiled  on  the  outside 
of  the  armature  wires  to  preclude  the  separation, 


ELECTRICAL  DICTIONARY  15 

by  centrifugal  force  of  the  armature  wires  from  the 
core. 

Armature  Bore. — The  space  allowed  for  the  rotation  of 
an  armature  between  the  pole  pieces  of  a  dynamo. 

Armature  Core. — The  body  of  laminated  iron  which 
carries  the  coil  conductors  of  dynamos  and  motors. 

Armature  Loop. — The  single  conducting  loop  on  a  dyna- 
mo armature. 

Armature  of  Dynamo. — An  iron  core  around  which  is 
wound  coils  of  insulated  wire.  That  part  of  a  dyna- 
mo which  generates  useful  currents  or  differences 
of  potential.  The  part  of  a  dynamo  which  rotates 
between  the  field  magnets  or  pole  pieces.  That  part 
of  the  dynamo  which  generates  E.  M.  Fs.  by  the 
magnetic  flux  successively  filling  and  emptying  the 
coils. 

Armature  Pinion. — A  wheel  with  teeth  attached  to  the 
armature  shaft  of  a  surface  car  motor,  whose  func- 
tion is  to  engage  the  teeth  of  the  reducing  gear. 

Armature  Pockets. — Spaces  allowed  in  the  core  of  an 
armature  to  receive  the  armature  coils. 

Armature  Projections. — The  sections  of  an  armature 
core  which  intervene  between  the  slots  and  pockets. 

Armature  Reaction. — The  reactive  magnetic  effect,  re- 
sulting from  the  action  of  the  current  in  the  arma- 
ture of  a  dynamo,  on  the  magnetic  circuit  of  the 
machine. 

Armature  Slots. — The  slots  in  an  armature  core  in- 
tended to  receive  the  armature  coils. 

Armature  Spider. — A  frame-work  of  metal  attached 
with  keys  to  the  armature  shaft  and  equipped  with 


16  ELECTRICAL  DICTIONARY 

arms  projecting  radially  and  serving  to  hold  the 
armature  cores  solidly. 

Armature  Stampings. — Stampings  of  sheet  iron  em- 
ployed for  the  core  discs  on  laminated  armature 
cores. 

Armature  Varnish. — A  varnish  with  insulating  prop- 
erties used  on  armature  windings  to  increase  their 
resistance  against  friction  and  moisture. 

Armored. — Protected  by  armor,  as  of  cables  protected 
by  sheathing. 

Artificial  Illumination. — Light  obtained  from  artificial 
sources. 

Astatic. — Having  no  magnetic  power  of  direction. 

Astatic  Galvanometer. — A  galvanometer  equipped  with 
an  astatic  needle. 

Asynchronous. — Happening  or  acting  without  simul- 
taneity. 

Asynchronous  Alternating-Current  Motor. — A  motor, 
the  speed  of  which  is  not  simultaneous  with  that  of 
its  driving  generator ;  the  two  machines  having  an 
equal  number  of  poles. 

Atmosphere. — The  entire  mass  of  aeriform  fluid  sur- 
rounding the  earth.  The  weight  or  pressure  of  gas 
or  fluid  on  a  unit  of  surface:  14.73  pounds  per 
square  inch  at  sea  level. 

Atmospheric  Electricity. — Electricity  free  in  the  atmos- 
phere. 

Atom. — An  ultimate  particle  of  matter — the  smallest 
particle  of  simple  matter. 

Atomic. — Pertaining  to  or  consisting  of  atoms. 

Atomize. — The  separation  with  an  atomizer  of  a  fluid 
into  a  spray.  To  reduce  to  atoms. 


ELECTRICAL   DICTIONARY  17 

Attachment  Plug. — A  plug  introduced  into  a  screw 
socket,  or  spring  jack,  to  facilitate  the  connection 
of  lamps,  etc.,  to  a  circuit. 

Attract. — To  draw  to. 

Attraction  of  Gravitation. — The  attraction  of  force  by 
which  all  bodies  or  particles  of  matter  in  the  uni- 
verse tend  toward  each  other.  The  attraction  of 
the  earth  which  causes  all  bodies  of  lesser  mass 
within  its  influence  to  fall  upon  it. 

Attractions  and  Repulsions  of  Currents. — The  attrac- 
tion or  repulsion  exerted  by  active  circuits  upon 
one  another,  due  to  the  mutual  action  of  their  mag- 
netic fields. 

Aurora. — A  luminous  meteoric  phenomenon  appearing 
only  in  the  night,  displaying  itself  in  streams  and 
flashes  of  light,  ascending  toward  the  zenith  from  a 
•dusky  bank  a  few  degrees  above  the  northern  hori- 
zon. 

Aurora  Australis. — A  light  similar  to  the  Aurora  Bore- 
alis,  appearing  in  the  southern  skies. 

Aurora  Borealis. — The  northern  light. 

Automatic  Make-and-Break. — A  contrivance  which  en- 
ables the  to-and-fro  movement  of  the  armature  of 
an  electric  magnet  to  make  and  break  its  circuit 
automatically. 

Automatic  Overload- Switch. — An  automatic  electro- 
magnetic switch  introduced  in  a  circuit  which 
causes  it  to  open  automatically  when  the  discharg- 
ing current  surpasses  a  fixed,  safe  limiting  force. 

Automatic  Regulation  of  Dynamo — Electric  Machine. — 
That  regulation  of  a  dynamo  electric  machine 
which  automatically  maintains,  invariable,  the 


18  ELECTRICAL  DICTIONARY 

strength  of  current,  or  the  potential  difference  at 
the  terminals. 

Automatic  Regulation  of  Motor. — That  regulation  of  a 
motor  which  preserves  its  speed  constant. 

Automatic  Circuit-Breaker. — A  contrivance  by  means 
of  which  a  circuit  it  automatically  opened  when 
carrying  an  excessive  current. 

Automatic  Cut-Out  for  Storage  Battery. — An  automatic 
electro-magnetic  switch,  introduced  into  a  storage 
battery's  charging  circuit,  in  order  that  the  charg- 
ing circuit  may  be  opened  in  case  the  current  fails 
to  enter  the  batteries. 

Automatic  Fire-Alarm. — A  device  so  adjusted  as  to 
telegraph  automatically  an  alarm  of  fire  from  any 
place  when  its  temperature  is  increased  above  a 
certain  degree. 

Automatic  Telephone  Exchange. — A  telephonic  ex- 
change operated  upon  a  system  which  enables  the 
subscribers  to  communicate  with  each  other  in- 
dependent of  an  operator. 

Automatic  Telephone  Hook. — A  telephone  switch  which 
operates  automatically  when  the  receiver  is  taken 
off  or  hung  upon  it. 

Automatic  Time  Cut-Out. — A  contrivance  for  automat- 
ically cutting  a  translating  device  or  a  source  of 
electric  power  from  a  circuit  after  the  expiration 
of  a  certain  predetermined  time. 

Automobile. — Containing  the  power  of  self  movement. 

Automobile  Torpedo. — A  torpedo  containing  the  power 
to  propel  itself. 

Auxiliary  Bus. — An  auxiliary  pressure  to  which  a  cen- 


ELECTRICAL  DICTIONARY  19 

tral  station  bus-bar  is  connected.  Not  the  main 
station  pressure ;  but  one  differing  from  it. 

Average  Efficiency  of  Motor. — The  efficiency  of  an  elec- 
tric motor  founded  on  its  mean  load.  The  ratio  of 
a  motor's  performance  in  a  specified  time  to  the 
electric  power  it  has  consumed  in  the  same  time. 

Average  Life  of  Incandescent  Lamp. — The  average 
length  of  time  that  a  number  of  incandescent 
lamps,  on  a  circuit  of  specified  pressure,  will  burn 
without  breakage. 


B.  S.  G. — An  abbreviation  of  British  standard  gauge. 
B.  &  S.  W.  G. — An  abbreviation  of  Brown  and  Sharp 's 

wire  gauge. 

B.  T.  U. — An  abbreviation  of  British  thermal  unit. 
B.  W.  G. — An  abbreviation  of  Birmingham  wire  gauge. 
Back  Pitch. — The  pitch  backward  of  the  windings  of  an 

armature. 

Back-Turns  of  Armature. — Turns  of  an  armature  cur- 
rent which  have  a  tendency  to  demagnetize  the 
field.  Back  ampere  turns. 

Backward  Pitch  of  Armature  Windings. — A  pitch  in- 
variably left-handed  when  viewed  from  commuta- 
tor side. 

Bad  Earth. — A  name  given  to  a  bad  ground,  or  an  earth 
connection  with  a  comparatively  strong  electric  re- 
sistance. 

Baking  Oven,  Electric. — A  bake  oven  heated  by  elec- 
tricity. 


20  ELECTRICAL  DICTIONARY 

Balance  Photometer. — A  photometer  founded  on  the 
dissolution  of  iodide  of  nitrogen  by  the  process  of 
light  action. 

Balanced  Armature. — An  armature  having  its  weight 
apportioned  with  regularity  as  referred  to  its  axis 
of  rotation.  An  armature  set  in  order  by  the  use 
of  additional  weights,  so  that  its  weight  is  appor- 
tioned uniformly  as  referred  to  its  axis  of  rotation. 

Balanced  Load. — A  load  uniformly  apportioned  to  two 
or  more  generating  units  as  observed  in  the  poly- 
phase systems  of  distribution,  or  the  three-wire, 
five-wire,  multiple. 

Balanced  Polyphase  System. — A  polyphase  system  with 
all  its  branches  proportional  with  reference  to  their 
electro-motive  force  and  phase. 

Balanced  Resistance. — A  resistance  arranged  in  a 
bridge  in  such  a  manner  that  it  will  be  balanced 
by  the  residuary  resistance  in  the  bridge. 

Balancing  Coil  of  Armature. — A  subsidiary  field-wind- 
ing in  series  with  an  armature  with  its  magneto-mo- 
tive force  equal  and  opposite  to  that  of  the  arma- 
ture current,  obtaining  zero  as  the  total  magnetic 
effect  upon  the  field,  leaving  the  field  flux  un- 
changed no  matter  what  the  load. 

Balancing  Resistance  for  Dynamos. — A  governing  re- 
sistance possessing  a  range  adequate  to  the  balan- 
cing of  one  dynamo  against  another  with  which  it 
is  worked  in  parallel. 

Bank  of  Lamps. — An  assemblage  of  electric  lamps  to- 
gether in  a  common  structure,  ordinarily  with  a 
view  to  acquiring  a  load. 

Bank  of  Transformers. — An  assemblage  of  transformers 
together  in  a  common  structure,  ordinarily  with  a 


ELECTRICAL  DICTIONARY  21 

view,  either  to  acquire  a  load,  or  to  modify  the 
pressure. 

Bar  Armature. — An  armature  the  conductors  of  which 
are  constructed  of  bars-. 

Bar  Electro-Magnet. — An  electro-magnet  with  its  core 
presenting  the  appearance  of  a  straight  bar  or 
rod. 

Bar  Windings. — Armature  windings  constructed  of 
copper  bars. 

Bar- Wound  Armature. — An  armature  the  conductors  of 
which  have  the  shape  of  bars. 

Bare  Carbons. — Arc  light  carbons  which  are  not  electro- 
plated with  copper. 

Barometer. — An  instrument  for  determining  the  weight 
or  pressure  of  the  atmosphere. 

Barometric  Column. — A  column  ordinarily  of  mercury, 
about  30  inches  in  perpendicular,  supported  in  a 
barometer  by  the  pressure  of  the  atmosphere. 

Bar  Winding  of  Armature. — A  winding  composed  of 
copper  bars  joined  together  at  their  extremities  and 
insulated. 

Basis  Metal  of  Electro-Plating. — A  metal  upon  the  sur- 
face of  which  a  deposit  is  to  be  made  by  electro- 
plating. 

Battery. — A  term  often  applied  to  an  electric  battery. 

Battery  Gauge. — A  movable  galvanometer  appropriate 
for  common  battery-testing  work. 

Battery  Jar. — A  jar  employed  to  hold  the  electrolyte 
of  each  separate  cell  of  a  primary  or  secondary  bat- 
tery. 

Battery  Lamp. — An  incandescent  lamp  which  by  reason 


22  ELECTRICAL  DICTIONARY 

of  its  low  voltage  can  be  worked  by  the  voltage  of 
a  battery  having  a  few  series-connected  cells. 

Battery  Motor. — An  electric  motor  wound  in  such  man- 
ner as  to  admit  of  operation  by  a  comparatively 
low  power,  such  as  that  of  the  common  battery. 

Battery  of  Generators. — Several  generators  connected 
in  such  manner  as  to  obtain  the  action  of  a  single 
generator. 

Battery  Solution. — The  fluid  or  electrolyte  of  the  pri- 
mary or  secondary  cell. 

Battery  Syringe. — A  syringe  employed  for  emptying  a 
voltaic  battery  of  acids  or  liquids  which  have  lost 
their  potency,  or  for  replenishing  it  with  live  liquid. 

Becquerel  Radiation. — A  radiation  discovered  by  Bec- 
querel,  which  is  invisible  and  which  is  given  out  by 
some  salts,  notably  salts  of  uranium,  and  which  has 
the  power  to  permeate  many  opaque  bodies  im- 
penetrable by  ordinary  light,  and  affecting  a  photo- 
graphic plate. 

Bega. — The  prefix  for  one  billion,  one  thousand  million 
or  109. 

Beg-Ohm. — A  billion  ohms.    One  thousand  megohms. 

Bell-<Hanger's  Joint. — A  joint  made  by  looping  the  ends 
of  wires  into  each  other. 

Bell-Shaped  Magnet. — A  horse-shoe  magnet  as  if 
fashioned  from  a  section  of  split  pipe,  the  approach- 
ed poles  being  semi-circular. 

Belt-Driven  Generator. — A  generator  operated  with  a 
belt  instead  of  a  direct  or  rope-operated  generator. 

Belt,  Electric. — A  body  belt  supposed  to  consist  of  vol- 
taic or  thermo-electric  couples  and  used  for  certain 
assumed  therapeutic  efficacy. 


ELECTRICAL  DICTIONARY 


23 


Belt  Speed. — The  rapidity     of  a  belt's  movement  in 

transmitting  power. 
Bichromate  Voltaic  Cell. — A  zinc-carbon  couple  used 

with  bichromate  of  potash  and  sulphuric  acid  in 

aqueous  solution. 
Bicro. — The  prefix  for  a  one-billionth,  a  one  thousand 

millionth  of  109. 

Bicro- Ampere. — A  billionth  of  one  ampere. 
Bight  of  Cable. — One  loop  or  bend'  only  of  cable. 

Binding  Coils  or  Binding  Wires. —  Coils  of  wire  with 
which  the  outside  of  an  armature  is  bound  at  right 
angles-to  it,  to  obviate  the  loosening  of  the  arma- 
ture coils  by  centrifugal  force  while  the  member  is 
in  rotation. 

Binding  Post. — A  binding  screw  of  metal  solidly  fas- 
tened to  a  machine  to  facilitate  the  making  of  se- 
cure electric  connection. 

Biograph. — A  machine  which  reproduces  on  a  screen 
the  actual  movements  of  objects  by  the  exhibition 
of  pictures  in  rapid  succession. 

Bipolar. — Possessing  two  poles. 

Bipolar  Armature-Winding. — An  armature-winding 
adaptable  to  service  in  a  bipolar  field. 

Bipo  Armature-Winding. — An  armature-winding  adapt- 
able to  service  in  a  bipolar  field. 

Bipolar  Generator. — A  dynamo-electric  machine  having 
two  poles. 

Bipolar  Magnetic  Field. — A  magnetic  field  consisting  of 
two  opposed  magnetic  poles. 

Birmingham  Wire  Gauge. — A  wire  gauge  used  hi  Eng- 
land. 


24  ELECTRICAL  DICTIONARY 

Black  Electro-Metallurgical  Deposit. — A  black  electro- 
metallurgical  deposit  precipitated  from  the  metal 
in  a  plating  bath  and  due  to  the  use  of  a  current 
of  excessive  strength. 

Blake  Telephone  Transmitter. — A  style  of  carbon  trans- 
mitter. 

Blasting,  Electric. — The  explosion  of  powder  or  other 
explosives  in  a  blast  by  means  of  electric  ignition. 

Blavier's  Test. — The  localizing  of  a  single  fault  on  a 
single  telegraph  line  or  conductor  by  means  of  the 
test  brought  into  practice  by  Blavier,  and  which  is 
accomplished  by  gauging  the  resistance  at  one  end, 
while  the  other  end  is  alternately  freed  and 
earthed. 

Block  System  for  Railroads. — A  system  of  block  signals 
employed  in  railroad  train  service  to  prevent  col- 
lisions ;  the  road  being  divided  into  sections  of  cer- 
tain lengths,  with  towers  situated  at  the  end  of 
these  sections,  having  telegraphic  intercommuni- 
cation, providing  for  the  display  of  proper  signals, 
thereby  preventing  more  than  one  train  or  engine 
from  occupying  the  same  section  or  block  at  the 
same  time. 

Blow. — To  fuse  -a  safety  fuse. 

Blowing  a  Fuse. — The  melting  or  fusing  of  a  safety 
fuse  resulting  from  the  passage  of  the  current 
through  it  exceeding  the  carrying  capacity  of  the 
strip. 

Blowing  Point  of  Fuse. — That  degree  of  current 
strength  which  melts  or  blows  the  fuse. 

Bobbin,  Electric. — A  coil  of  wire,  insulated,  and  adapt- 
able to  an  electric  current  employed  for  any  pur- 
pose— for  instance :  in  energizing  electro-magnets. 


ELECTRICAL  DICTIONARY  25 

Bolometer. — A  machine  to  measure  minute  differences 
by  means  of  electricity.  A  thin  wire  or  strip,  the 
resistance  of  which  is  modified  incident  radiant 
energy. 

Bonded  Rails. — Rails  which  are  used  in  an  electric  sys- 
tem as  a  section  of  the  current,  and  which  are 
properly  jointed  at  their  ends  in  order  to  insure 
perfect  electric  contact. 

Bonding  Resistance  of  Rail. — The  resistance  presented 
at  the  bonded  joints  of  a  rail  circuit. 

Booster. — An  auxiliary  electric  dynamo  placed  in  a  par- 
ticular feeder  or  assemblage  of  feeders  in  a  distrib- 
uting system  in  order  to  increase  the  pressure 
of  that  particular  feeder  or  assemblage  beyond  the 
pressure  of  the  rest  of  the  system. 

Boring1,  Electric. — Making  holes  in  metals  with  voltaic 
arc  heat. 

Bougie-Decimale. — The  standard  candle  of  France. 

Bougie-Metre. — The  unit  of  illumination,  frequently 
termed  a  lux,  and  equal,  at  a  distance  of  one  metre, 
to  the  illuminating  power  of  a  bougie-decimale. 

Box  Bridge. — An  electric  bridge  in  which  the  two  arms 
together  with  the  ascertained  resistance,  consists 
of  standard  resistance  coils  inclosed  in  a  box. 

Boxing  the  Compass. — Calling  in  consecutive  order  the 
names  of  the  points  of  the  compass,  beginning  at 
any  given  point. 

Brake  Arm. — A  lever  by  which  the  power  is  applied  to 
a  brake  shoe,  to  which  it  is  connected. 

Brake  Shoe. — A  metal  casting  conforming  in  shape  to 
an  arc  of  the  car  wheel  circumference,  and  which 


26  ELECTRICAL  DICTIONARY 

is  pressed  against  the  wheel  by  the  operation  of 
the  connected  lever  in  order  to  stop  the  car. 

Braided  Wire. — A  wire  insulated  with  a  cover  of 
braided  material. 

Branch. — Any  conductor  in  a  system  of  parallel  dis- 
tribution into  which  taps  and  outlets  are  made. 

Branch  Block. — A  block  of  porcelain  with  grooves  into 
which  the  terminals  or  conductors  are  put  to  make 
a  connection  to  the  mains  with  a  pair  of  branch 
wires. 

Branch  Circuits. — Extra  circuits  located  at  points  of 

a  circuit  at  which  the  current  branches,  where  some 

of  the  current  flows  through  the  branch  and  the 

rest  passes  through  the  initial  circuit. 
Branch  Coupling  Box. — A  coupling  box  adaptable  to 

making  a  connection  for  house  service  with  the 

mains  supplying  the  house. 
Branch  Cut-Out. — A  safety  fuse   introduced  between 

two  branch  wires  and  the  mains  from  which  they 

receive  their  supply. 

Branch  Fuse. — A  safety  fuse  or  branch  cut-out. 
Branding,  Electric. — The  heating  to  incandescence  of 

a  branding  implement  electrically  instead  of  in  the 

usual  way. 

Breadth  Coefficient  of  Armature  Coil. — The  relation  of 
the  efficient  electro-motive  force  induced  in  an  ar- 
mature coil  to  that  which  would  be  induced  in  a 
coil  with  breadth ;  that  is  to  say,  if  the  whole  of  it 
were  compressed  to  occupy  the  space  of  a  single 
turn  only. 

Break. — Any  failure  of  the  continuous  conductivity  in 
a  circuit. 


ELECTRICAL,  DICTIONARY  27 

Break-Down  Switch. — A  panel  switch,  used  for  connect- 
ing the  positive  and  negative  bus-bars  in  a  little 
three-wire  system  in  order  that  it  may  be  trans- 
formed into  a  two-wire  system,  so  that  in  the  event 
of  a  break-down  the  system  can  be  supplied  with 
a  current  from  one  dynamo  only. 

Breaking1  Capacity  of  Switch. — The  strength  of  current 
which  a  switch  is  capable  of  interrupting  safely,  as 
distinguished  from  its  carrying  capacity. 

Breaking  Down  of  Dielectric. — The  weakening  of  a 
dielectric  under  electric  pressure  which  allows  dis- 
integrating discharges  to  pass  through  its  sub- 
stance. 

Breaking  Down  of  Insulation. — The  impotency  of  in- 
sulating material  manifested  in  the  disruptive  pass- 
age through  it  of  an  electric  discharge. 

Breaking  In. — The  interruption  of  a  telegraph  message 
in  transmission  between  two  points  by  the  attempt 
of  an  intermediate  operator  to  use  the  line  at  the 
same  time. 

Bridge,  Electric. — A  device  employed  to  measure  an 
unknown  electric  resistance.  A  contrivance  used 
to  measure  unknown  resistances  by  comparison 
with  adjustable  ones. 

Bridge-Wire. — A  wire  in  a  Wheatstone's  Bridge  in 
which  the  galvanometer  is  set. 

Bridging-Bell  Telephone  System. — A  telephonic  system 
of  communication  where  the  call  bells  are  arranged 
in  multiple  arc  and  by  which  the  two-line  conduc- 
tors of  metallic  circuit  are  permanently  bridged  to 
the  ground  in  grounded  circuits;  thus  a  call  sent 
out  rings  every  bell  in  the  line,  indicating  by  means 
of  a  code  of  signals  the  particular  station  needed. 


28  ELECTRICAL  DICTIONARY 

Bright  Deposit. — A  shining  surface  of  metallic  deposit 
resulting  from  a  special  final  process  in  the  electro- 
plating of  silver. 

Brother-in-Law. — A  concealed  bell,  corresponding  in 
sound  with  that  of  the  fare  indicator,  and  rung  in- 
stead of  the  car  indicator  bell,  by  dishonest  con- 
ductors, when  fares  have  been  collected. 

Brush  Contact-Surface. — The  part  of  the- surface  of 
a  commutator  which  is  at  any  instant  of  time  in 
contact  with  the  brushes. 

Brush-Holder  Cable. — A  stranded  conductor  used  in  a 
dynamo  or  motor  to  obtain  direct  connection  with 
the  brushes. 

Brush  Holders  for  Dynamo-Electric  Machine. — Contri- 
vances by  means  of  which  the  collecting  brushes  of 
a  dynamo-electric  machine  are  supported. 

Brush  Rocker. — A  contrivance  in  a  dynamo  which 
serves  to  shift  the  brushes  on  the  commutator 
from  one  position  to  another. 

Brush  Shifting  Device. — A  modified  style  of  brush 
rocker. 

Brushes  of  Dynamo-Electric  Machines. — An  assem- 
blage of  wires  in  a  bundle,  narrow  piece  of  metal, 
carbon  plates  or  metallic  plates  slit,  which  press 
against  the  commutator  cylinder,  carrying  off  the 
current  generated. 

Bucking. — A  term  expressing  the  action  of  a  street  car 
when  it  stops  suddenly,  as  though  it  had  collided 
with  another  car,  and  resulting  from  the  opposition 
between  two  motors. 

Buckled  Diaphragm. — A  defect  in  the  transmitter  or  re- 
ceiver of  a  telephone  caused  by  warping  of  the  dia- 
phragm. 


ELECTRICAL   DICTIONARY  29 


Buckling. — A  warping  in  the  surface  of  the  storage 
cell  plates  due  to  a  too  rapid  discharge. 

Bug. — In  quadruplex  telegraphy,  a  term  serving  to 
designate  any  defect  in  the  working  of  the  appara- 
tus. Usually  applied  to  a  defect  in  the  working  of 
any  electric  apparatus. 

"Building-Up"  of  Dynamo. — The  action  by  which  a 
dynamo-electric  machine,  after  starting  up,  speed- 
ily attains  its  maximum  E.  M.  F. 

Bullet  Probe. — A  probe  with  electric  conductors  ad- 
justed in  such  manner  as  to  effect  the  closing  of 
an  electric  circuit  and  the  operation  of  an  electric 
signal  when  the  probe  comes  in  contact  with  the 
bullet. 

Bunched  Cable. — A  cable  having  more  than  one  wire 
or  conductor. 

Bunsen  Screen. — The  screen  of  a  Bunsen  photometer. 

Buoy,  Electric. — A  buoy  displaying  luminous  signals 
produced  by  electricity. 

Burette. — A  graduated  glass  tube  with  a  small  aperture 
and  stop  cock  used  to  deliver  measured  quanti- 
ties of  liquid. 

Buried  Cable  or  Conductor. — A  cable  placed  under- 
ground, directly  in  the  earth,  and  not  in  a  conduit 
or  subway. 

Burn-Out. — The  damage  sustained  by  an  armature  or 
any  member  of  an  electric  machine  resulting  from 
an  excessive  current  due  to  short  circuit  and  differ- 
ent causes. 

Burned-Out  Incandescent  Lamp. — An  incandescent 
lamp  which,  by  reason  of  long  continued  service, 
has  lost  its  capacity  to  furnish  light. 


30  ELECTRICAL  DICTIONARY 

Burning  at  Commutator  of  Dynamo. — An  arcing  effect 
at  the  brushes  of  a  dynamo-electric  machine  arising 
from  poor  contact  or  imperfect  position,  by  reason 
of  which  the  circuit  loses  energy  and  the  commuta- 
tor segments  or  brushes  are  destroyed. 

Bus-Bar  Connectors. — Connectors  used  to  connect  or 
unite  the  ends  of  bus-bars. 

Bus-Bars. — Bars  which  receive  the  entire  current  gen- 
erated and  which  are  composed  of  heavy  conduct-i 
ing  metal  and  connected  directly  with  the  poles 
of  one  or  several  dynamo-electric  machines. 

Butt  Joint. — A  joint  made  by  soldering  the  wires  to- 
gether end  to  end. 

Buzzer,  Electric. — A  call  emitting  a  buzzing  sound  ob- 
tained by  the  use  of  a  rapid  automatic  contact- 
breaker. 


C. 


C.  G.  S. — An  abbreviation  of  centimetre-gramme-second 

C.  P. — An  abbreviation  of  candle-power. 

C.  G.  S.  Units. — Centimetre-gramme-second  units. 

Cable. — A  cable  for  conveying  electricity.    A  message 

sent  through  an  electric  cable. 
Cable  Box. — A  box  employed  to  receive  and  protect  i 

cable  head. 
Cable  Drum. — A  drum  in  machinery  for  handling  cabl( 

and  upon  which  it  is  wound,  keeping  it  in  mos" 

convenient  shape  for  shipping,  laying,  etc. 
Cable  Head. — A  board,  rectangular  in  form,  and  equip 

ped  with  binding  posts  and  fuse  wires,  used  to  re 


ELECTRICAL  DICTIONARY  31 

ceive  the  wires  'at  the  point  where  they  enter  a 
cable  in  overhead  lines. 

Cable  Tank. — A  stout  water-tight  tank  carried  on  a 
cable  ship  and  which  serves  to  hold  a  section  of 
cable  coil  which  is  ready  to  lay. 

Cable  Transformer. — A  transformer  of  alternating  cur- 
rent, the  primary  and  secondary  conductors  of 
which  are  formed  like  a  cable  covered  with  an 
iron  sheath  or  magnetic  circuit. 

Cadmium  Standard  Cell. — A  standard  voltaic  cell 
showing  an  exceedingly  low  temperature  coefficient 
of  change  in  E.  M.  F.  and  using  a  cadmium-zinc 
couple. 

Calculagraph. — A  machine  for  recording  the  time  that 
the  line  is  used  by  a  subscriber  when  communica- 
ting by  long  distance  telephone. 

Cal-Electric  Generator. — A  generator  the  performance 
of  which  is  contingent  upon  the  generation  of  the 
electric  fluid  in  the  secondary  coil  of  a  transformer, 
effected  by  variation  of  temperature  in  the  iron 
core  of  transformer. 

Cal-Electricity. — The  electricity  in  the  iron  core  of  a 
transformer  resulting  from  change  of  temperature. 

Calibrate. — To  ascertain  the  complete  or  relative  values 
of  the  indications  of  electrical  instruments,  i.  e. : 
voltmeters,  electrometers,  galvanometers,  watt- 
meters, etc. 

Calibrating. — Ascertaining  and  designating  the  values 
or  indications  of  a  voltmeter,  electrometer,  galvano- 
meter, wattmeter,  etc. 

Call-Bell,  Electric. — An  electric  bell  employed  to  at- 
tract the  attention  of  an  operator  and  advise  him 


32  ELECTRICAL  DICTIONARY 

that  he  is  wanted  at  the  instrument  for  communi- 
cation. 

Calling  Drops. — A  drop  used  to  indicate  the  person 
calling  and  employed  in  isolated-station  switch- 
boards. 

Calling  Plug. — The  one  of  two  plugs  at  a  central  station 
which  is  put  into  the  jack  of  a  subscriber  who  is 
called  for  and  through  which  he  is  signaled  to  the 
telephone. 

Calorescence. — The  change  of  heat  rays,  which  are  in 

an  obscure  state,  into  luminous  rays  by  impact  with 

solid  bodies. 
Caloric. — A  term  applied  formerly  to  the  principle  of 

heat  or  the  agent  to  which  the  phenomena  of  heat 

and  combustion  were  ascribed. 

Calorie. — A  unit  of  heat.  The  degree  of  heat  necessary 
to  raise  1  gramme  of  water  1  degree  centigrade. 

Calorific  Intensity. — The  temperature  reached  in  com- 
bustion. 

Calorimeter. — An  apparatus  for  measuring  the  amount 
of  heat  contained  in  bodies.  - 

Calorimetric  Conductivity. — The  conductivity  of  a  sub- 
stance founded  upon  the  amount  of  heat  transfer- 
red in  a  specified  time,  without  considering  the 
temperature  reached. 

Candle. — A  unit  of  photometric  energy.  The  photo- 
metric energy  equal  to  the  product  of  a  standard 
candle  burning  at  a  rate  of  two  grains  a  minute. 

Candle-Foot. — A  unit  of  illumination  equal  at  a  dis- 
tance of  one  foot  to  that  which  is  given  out  by  a 
standard  British  candle. 


ELECTRICAL  DICTIONARY  33 

Candle-Power. — The  intensity  of  light  given  out  by  a 
lucid  body  calculated  by  standard  candles.  The 
photometric  energy  of  one  standard  candle. 

Canopy  Switch. — A  switch  located  overhead  at  each  end 
of  a  trolley  car  which  enables  the  motorman  to  turn 
the  current  on  or  off  the  car  at  will. 

Caoutchouc. — A  vegetable  substance  obtained  from  the 
juice  of  certain  tropical  trees  valued  for  its  superior 
insulating  properties.  Commercial  india-rubber. 

Capability  of  Dynamo-Electric  Machine. — The  maxi- 
mum energy  in  theory,  of  a  dynamo  obtained  by 
dividing  the  square  of  its  electromotive  force  by 
its  resistance. 

Capacity  of  Accumulator. — The  product  of  a  storage 
battery  expressed  in  watt-hours  -or  ampere-hours. 

Capacity  of  Condenser. — The  quantity  of  electricity 
that  a  condenser  can  hold  in  coulombs  when- 
charged  to  a  one-volt  pressure. 

Capillarity. — The  rise  and  fall  of  liquids  in  conduits, 
the  inside  diameters  of  which  are  very  small. 

Capillary. — Resembling  a  hair;  fine  minute,  small  in 
diameter. 

Capillary  Attraction. — The  cause  which  determines  the 
ascent  or  descent  of  a  fluid  in  a  capillary  tube  above 
or  below  the  'surrounding  fluid. 

Capsizing  Thermometer. — A  thermometer  for  deep-sea 
soundings,  used  in  cable  work,  the  position  of 
which  is  reversed  or  upset  when  the  lead  begins 
to  ascend  from  the  bottom,  thereby  securing  a 
record  of  the  temperature. 

Car  Body. — All  that  part  of  a  railroad  car  resting  upon 
the  trucks,  and  designed  for  the  accommodation  of 
passengers.  A  frame-work  of  wood. 


34  ELECTRICAL  DICTIONARY 

Car  Controller. — A  contrivance  employed  to  control  the 
movement  of  a  trolley  car  and  which  is  placed  at 
each  end  of  the  car  in  order  that  the  motor  can 
readily  -stop,  reverse,  and  regulate  the  speed  of  the 
car. 

Car  Heater,  Electric. — A  heater  deriving  its  heat  supply 
from  the  action  of  electricity  and  composed  of  coils 
of  insulated  wire  crossed  by  an  electric  current. 

Car-Lamp,  Electric. — An  incandescent  lamp  used  in 
street  railway  cars,  and  ordinarily  supplied  with  an 
anchored  filament. 

Car  Truck. — That  part  of  a  car  which  carries  and  sus- 
tains the  weight  of  the  body. 

Carbon. — An  elementary  substance,  not  metallic,  in  na- 
ture, which  predominates  in  all  organic  compounds 
and  occurs  in  three  distinct  allotropic  forms :  black 
lead,  charcoal  and  the  diamond. 

Carbon  Brushes  for  Electric  Motors  or  Generators. — 

Artificial  carbon  plates  used  as  brushes  for 
dynamos  or  motors. 

Carbon  Diaphragm  of  Telephone. — A  light  sheet  of 
metal  serving  as  a  diaphragm  in  some  forms  of 
transmitters. 

Carbon  Electrodes  for  Arc  Lamps. — The  carbons  be- 
tween which  the  arc  of  an  electric  arc  lamp  is  main- 
tained. 

Carbon  Holder. — A  device  used  in  arc  lamps  to  support 
the  carbon. 

Carbon  Motor  Brush. — A  carbon  brush  used  on  a  motor. 

Carbon-Point  Lightning-Arrester. — An  arrester  where- 
in the  disruptive  discharge  occurs  between  opposed 
carbon  points. 


ELECTRICAL  DICTIONARY  35 

Carbon  Rheostat. — A  resistance  formed  of  carbon 
plates  and  powder  and  adjusted  so  that  it  can  be 
modified  by  pressure. 

Carbon  Telephone  Transmitter. — A  telephone  trans- 
mitter the  operation  of  which  is  contingent  upon 
the  variation  in  resistance  of  a  carbon  button,  or  a 
quantity  of  loose  granulated  carbon,  on  the  back 
and  forth  movement  of  the  diaphragm. 

Carbonic  Acid  Gas. — A  gas  formed  by  the  uniting  of 
one  part  of  carbon  with  two  parts  of  oxygen. 

Carbonize. — To  convert  into  carbon  by  combustion,  by 
the  action  of  fire  or  concentrated  acids  on  carbon- 
izable  substances. 

Cardew  Voltmeter. — A  voltmeter  which,  by  means  of  a 
long  fine  wire  whose  expansion,  resulting  from  the 
passage  through  it  of  the  current  to  be  measured, 
makes  the  indication. 

Carrying  Capacity. — The  maximum  carrying  strength 

which  a  wire  is  capable  of  carrying. 
Case-Hardening1. — The    hardening    of    the    outside    of 

metals  with  heat  generated  by  electricity. 
Cast  Rail-Bond. — A  bonding  obtained  by  uniting  track 

rails   in   a   trolley   system  with   molten   iron   cast 

around  all  but  the  upper  part  of  the  joint. 

Catalysis. — An  influence  exerted  on  chemical  decom- 
position by  certain  substances,  which  produce 
changes  in  the  affinities  of  other  substances,  merely 
by  contact,  and  without  experiencing  any  changes 
themselves. 

Cataphoresis. — The  tendency  to  mix  or  become  equably 
diffused  as  referred  to  electricity.  Electric  osmose. 

Cataphoretic  Electrode. — An  electrode  which  holds  in 


36  ELECTRICAL  DICTIONARY 

solution  the  chemical  which  is  to   enter  into  the 
body  by  cataphoresis.    The  anode. 

Centenary  Curve. — The  curve  or  sag  formed  by  the 
weight  of  a  wire  hanging  freely  between  two 
points  of  suspension. 

Cathelectrotonus. — The  augmentation  of  functional 
activity  produced  in  a  nerve  in  the  vicinity  of  the 
negative  electrode  or  cathode,  in  the  practice  of 
electro-therapeutics. 

Cathode. — That  part  of  a  battery  by  which  the  electric 
current  leaves  substances  through  which  it  passes, 
or  the  surface  at  which  the  electric  current  passes 
out  of  the  electrolyte ;  the  negative  pole. 

Cathode  Rays. — Rays  emitted  by  the  cathode  or  nega- 
tive pole  of  an  X-ray  tube. 

Cathodogram. — A  picture   obtained  by  means   of  the 

X-ray. 
Cauterization. — The  act  of  searing  or  burning  with  fire, 

or  with  a  heated  object  or  caustic  substance. 

Cauterization,  Electric. — The  act  of  cauterizing  by  the 
application  of  an  electrically  heated  wire. 

Cautery  Battery. — A  term  in  electro-therapeutics  ap- 
plied to  a  multiple-connected  voltaic  battery 
suitable  for  producing  incandescence  for  cauteriz- 
ing purposes. 

Ceiling  Block. — Blocks  attached  to  the  ceiling,  from 
which  flexible  cords  can  be  suspended  and  con- 
nected with  the  supply  wires  of  an  incandescent 
system. 

Ceiling  Board. — A  board  attached  to  the  ceiling  from 
which  to  hang  arc  lights. 


ELECTRICAL  DICTIONARY  37 

Ceiling  Fan. — A  fan  suspended  from  the  ceiling  and 
driven  by  electric  power. 

Ceiling  Rosette. — An  ornamental  ceiling  block  in  form 
of  a  rose. 

Celluloid  Lamp-Filament. — A  filament  made  of  carbon- 
ized celluloid. 

Centi. — A  prefix  indicating  the  one  hundredth  part. 
Centi-Ampere. — The  one  hundredth  of  an  ampere. 

Centigrade  Thermometer  Scale. — A  thermometer  scale 
whose  thermometric  tube  is  divided  into  one  hun- 
dred equal  degrees  between  the  melting  point  of 
ice  and  the  boiling  point  of  water. 

Centimetre. — The  one  hundredth  of  a  metre.     0.3937 

inch. 
Centimetre-Gramme-Second  System. — A  system  taking 

the  centimetre  as  its  base  for  the  unit  of  length,  the 

gramme  for  the  unit  of  mass  and  the  second  for 

the  unit  of  time. 

Central. — A  term  applied  to  any  central  telephone  of- 
fice or  exchange. 

Central  Lighting-Station. — A  station  where  are  located 
the  generators  and  distributing  machinery  that 
furnish  the  current  to  the  lamps  in  a  certain  dis- 
trict. 

Central-Station  Lighting. — The  supplying  from  a  cen- 
tral station  of  the  current  which  lights  the  lamps 
in  a  manner  of  houses  and  structures. 

Central  Telephone  Exchange. — A  central  office  with 
which  a  number  of  subscribers  or  telephone  sta- 
tions are  connected.  A  central  exchange  with 
which  a  number  of  local  exchanges  are  connected. 


38  ELECTRICAL  DICTIONARY 

Cement-Lined  Conduit. — A  conduit  constructed  with 
any  suitable  material,  such  as  metal,  stone  or  wood, 
having  ducts  whose  surfaces  are  lined  with  cement. 

Centre  of  Distribution. — Any  point  in  an  incandescent 
distribution  system  where  the  supply  current  is 
branched  or  distributed  radially  to  mains,  sub- 
mains  or  transferring  devices. 

Centre  of  Gravity. — That  point  of  a  body  about  which 
all  its  parts  are  balanced. 

Centre  of  Oscillation. — That  point  of  a  body  which,  de- 
scribing the  movement  of  a  pendulum,  is  neither 
accelerated  nor  retarded  during  its  oscillatory 
movements  by  those  parts  of  the  pendulum  which 
are  located  above  or  below  it. 

Centre-Pole  Construction. — A  system  of  construction 
by  the  use  of  poles,  and  employed  in  double  track 
trolley  systems;  the  poles  being  set  between  the 
two  tracks  and  equipped  with  bracket  arms  which 
extend  over  the  tracks  and  from  which  the  trolley 
wire  is  suspended. 

Centrifugal  Force. — That  force  by  which  a  body  in 
rotary  motion  tends  to  fly  off  from  the  axis  of  mo- 
tion. 

Centrifugal  Governor. — A  device  serving  to  keep  con- 
stant the  speed  of  a  steam  engine  or  other  motor 
regardless  of  any  changes  in  its  load  or  perform- 
ance. 

Centrifuge. — An  apparatus  employed  in  the  separation 
of  fluids  differing  in  consistency  and  of  solids  from 
fluids  by  centrifugal  force. 

Centripetal. — Tending  toward  the  center. 

Change-Over  Switch. — A  switch  employed  in  a  central 


ELECTRICAL  DICTIONARY  39 

station  to  change  a  working  circuit  from  one  dyna- 
mo, or  battery  of  dynamos,  to  another. 
Characteristic  Curve. — A  diagram  in  which  the  relation 
of  varying  values  is  represented  by  a  curve.  A 
curve  which  shows  the  peculiar  properties  of  a 
dynamo  operating  under  various  phases. 

Characteristics  of  Sound. — Peculiarities  by  which  mu- 
sical sounds  are  distinguished  one  from  another, 
i.  e. :  pitch,  tone,  intensity,  quality,  loudness. 

Charged  Body. — A  body  which  is  charged  with  elec- 
tricity. 

Charging  Current. — A  current  used  to  charge  an  accu- 
mulator or  storage  battery. 

Chemical  Affinity. — The  attraction  of  one  atom  for  an- 
other. That  force  which  urges  atoms  to  combine 
and  produce  molecules. 

Chemical  Change. — The  formation  of  new  molecules  by 
any  change  in  matter  following  the  combustion  of 
atoms. 

Chemical  Effect. — That  effect  produced  by  atomic  com- 
bination in  which  the  individual  characteristics 
and  properties  of  the  substances  entering  into  such 
combination  are  lost.  A  combination  of  atoms 
through  which  new  molecules  are  formed. 

Chemical  Photometer. — A  photometer  which  deter- 
mines, by  the  amount  of  chemical  action  produced 
in  a  specified  time,  the  intensity  of  the  light  to  be 
measured. 

Chemical  Separation. — Chemical  dissolution  or  decom- 
position. 

Chloride  Storage  Cell. — A  term  applied  to  a  storage 
cell,  the  plates  of  which  are  made  of  grids  of  anti- 


40  ELECTRICAL  DICTIONARY 

monious  lead  molded  around  small  knobs  of  fused 
chloride  of  lead  and  which  are  transformed  into 
spongy  metallic  lead  and  lead  peroxide  on  the 
negative  and  positive  plates,  when  brought  under 
the  action  of  a  charging  current. 

Choking  Coil. — A  coil  of  wire  wound  in  such  manner  on 
a  core  of  iron  as  to  acquire  self-induction  to  a  high 
degree  when  employed  on  alternating  current  cir- 
cuits. 

Choking  Effect.— The  effect  resulting  from  the  obstruc- 
tion or  cutting  off  of  an  alternating  current  by  a 
choking  coil,  effected  with  a  smaller  loss  of  force 
than  it  would  accomplish  as  an  ohmic  resistance 
only. 

Chronograph,  Electric. — An  electric  apparatus  em- 
'  ployed  to  measure  and  register  small  intervals  of 
time  automatically. 

Cigar-Lighter,  Electric. — An  apparatus  employed  to 
light  cigars  by  electricity. 

Cinematograph. — A  biograph. 

Cipher  Code. — A  code  employing  arbitrary  words  to 
represent  other  words  or  phrases. 

Circuit  Breaker. — A  device  serving  to  open  or  break  a 
circuit. 

Circuit,  Electric. — The  path  covered  by  an  electric  cur- 
rent in  its  passage  through  a  conductor  from  its 
starting  point  back  again. 

Circular  Flux. — A  term  applied  to  the  concentric  circu- 
lar flux  surrounding  an  active  cylindrical  con- 
ductor. 

Circular  Mil. — A  unit  of  area  taken  to  measure  the 
cross-section  of  wires,  or  about  0.7854  square  mils. 
A  circle  area  of  one  mil  diameter. 


ELECTRICAL  DICTIONARY  41 

Circular  Millage. — The  area  of  wire  or  conductor  cross- 
sections  denoted  in  circular  mils. 

Circumferential  Speed. — The  velocity  of  a  point  on  the 
circumference  of  a  revolving  wheel  or  armature. 

Clearance. — That  space  in  a  dynamo  or  motor  between 
the  surface  of  a  revolving  armature  and  the  polar 
surface  of  the  field  magnets. 

Cleat  Wiring. — Fixing  electric  conductors  or  wires  to 
ceilings  or  walls  by  the  use  of  adaptable  insulating 
cleats. 

Clockwise  Motion. — A  motion  which  when  observed 
from  the  face  corresponds  with  the  rotary  motion 
of  the  hands  of  a  clock. 

Clockwork  Feed  for  Arc  Lamps. — An  arc  lamp  con- 
trivance providing  for  the  feeding  of  the  carbons. 
An  arrangement  of  wheel  work. 

Closed  Circuit. — A  circuit  completed. 

Closed-Coil  Armature. — An  armature  whose  coils  are 
not  on  open  circuit  while  rotating.  A  dynamo 
armature  the  coils  of  which  are  assembled  in  sec- 
tions and  so  connected  with  the  bars  of  a  commu- 
tator as  to  be  continuously  connected  in  a  closed 
circuit. 

Closed-Coil  Winding. — A  winding  providing  for  the 
connection  of  the  armature  coils  while  the  machine 
is  in  operation. 

Closed  Iron-Circuit  Transformer. — A  transformer  hav- 
ing a  core  which  makes  a  completed  magnetic  cir- 
cuit. A  transformer  which  is  iron-clad. 

Closed  Magnetic  Circuit. — A  magnetic  circuit  lying  en- 
tirely in  iron  or  other  material  which  is  highly  per- 
meable by  magnetic  energy. 


42  ELECTRICAL  DICTIONARY 

Clutch  for  Arc  Lamps. — A  form  of  clutch  for  arc  lamps 

to  hold  carbons. 
Clutching  Device. — A  device  used  to  hold  the  carbons 

in  an  arc  lamp  or  for  holding  any  object  which  is 

subject  to  motion. 
Coarse  Winding  of  Field  Magnets. — The  series  winding 

of  a  compound  wound  machine. 

Coefficient  of  Expansion. — The  augmentation  in  the 
fractional  length  of  a  rod  or  bar  when  subjected 
to  heat  ranging  from  32  to  33  degrees  Pahr.  or  0  to 
1  degree  Cent. 

Coefficient  of  Hysteresis. — The  work  given  out  in  the 
cubic  centimetre  of  iron  or  any  magnetic  material 
during  one  cycle  of  unit  magnetic  flux  density. 
The  coefficient  from  which  is  obtained  the  hyster- 
etic  activity  when  it  is  multiplied  by  the  volume 
of  iron,  the  alternating  frequency  and  the  one- 
sixth  power  of  the  maximum  flux  density. 

Coefficient  of  Inductance. — A  fixed  quantity  which, 
multiplied  by  the  current  strength  flowing  through 
a  coil  or  circuit,  will  numerically  stand  for  the  flux 
linkage  with  such  coil  or  circuit  resulting  from 
that  current.  A  term  applied  at  times  to  coefficient 
of  self-induction. 

Coefficient  of  Reflection. — The  percentage  value  denot- 
ing the  ratio  of  intensity  of  a  reflected  ray  to  that 
of  an  incident  ray. 

Coercive  Force. — The  resisting  power  to  changes  in 
magnetization.  The  demagnetizing  power  which 
must  be  employed  to  completely  demagnetize  a 
magnetic  substance,  in  cyclic  magnetization. 

Coherer. — 'Conducting   particles    constituting    a    semi- 


ELECTRICAL,  DICTIONARY  43 

conducting  bridge  between  two  electrodes  and 
serving  to  detect  electro-magnetic  waves. 

Coil,  Electric. — A  coil  or  spool  of  insulated  wire  provid- 
ing for  the  passage  through  it  of  an  electric  cur- 
rent. 

Coked  Core  of  Incandescent  Filament. — A  filament  for 
incandescent  lamps,  the  core  of  which  is  electrical- 
ly coked  carbon  and  the  surface  of  which  is  coated 
with  a  carbon  deposit  by  the  flashing  process. 

Coked  Filament. — A  filament  of  carbon  for  incandes- 
cent lamps  which  has  been  freed  from  gases  and 
converted  into  a  variety  of  coke  by  being  subjected 
to  electric  heat  in  a  vacuum. 

Cold  Light. — Luminous  radiation  unattended  by  ob- 
scure radiation.  Fire-fly  or  glow-worm  light. 

Collecting  Brushes  of  Dynamo-Electric  Machine. — 
Brushes  which  press  against  the  commutator  cylin- 
der of  a  dynamo,  bearing  away  the  current  gen- 
erated in  the  armature  coils  by  the  E.  M.  F. 
•Brushes  which  press  on  the  collecting  rings  of  an 
alternating  current  armature. 

Collecting  Rings  for  Alternators. — Rings  of  metal 
which  are  connected  to  the  terminals  of  the  arma- 
ture coils  in  an  alternator  on  which  the  brushes 
that  carry  off  the  alternating  currents  are  in  con- 
tact. 

Collectors  of  Dynamo-Electric  Machine. — Brushes 
which  bear  on  the  commutator  cylinder  and  trans- 
late the  current  generated  by  rotation  of  the  ar- 
mature. 

Collectors  of  Frictional  Electric  Machine. — The  points 
of  metal  which  gather  the  charge  from  the  glass 
plate  or  cylinder  of  a  frictional  electric  machine. 


44  ELECTRICAL  DICTIONARY 

Collector  Rings — An  alternator's  collecting  rings. 

Combination  Fittings  for  Chandeliers. — Fittings  so  ar- 
ranged as  to  permit  the  use  of  both  electricity  and 
gas. 

Commercial  Efficiency. — That  energy,  termed  useful, 
produced  by  any  machine,  and  divided  by  the  total 
energy  it  takes  in. 

Commercial  Efficiency  of  Dynamo,  or  Generator. — The 

ratio  of  the  useful  electric  energy  of  a  dynamo  de- 
livered at  its  terminals,  divided  by  what  it  takes 
in  or  the  mechanical  power  required  to  drive  it. 

Commercial  Efficiency  of  Motor. — The  ratio  between 
the  electric  activity  taken  in  at  its  terminals  and 
the  mechanical  activity  developed  at  the  motor 
pulley. 

Commutator. — A  device  by  means  of  which  alternating 
currents  are  changed  into  continuous  ones  and  vice 
versa.  A  device  by  means  of  which  the  direction 
of  electromotive  currents  in  one  portion  of  a  cir- 
cuit is  changed  in  another. 

Commutator  Bar. — An  insulated  segment  of  a  commu- 
tator. 

Compass. — The  mariner's  compass. 

Compass  Card. — The  card  employed  in  the  mariner's 
compass  and  upon  which  is  indicated  the  four  car- 
dinal points  of  the  compass :  north,  south,  east  and 
west,  and  which  is  also  subdivided  into  32  points, 
termed  rhumbs,  and  also  divided  into  degrees  cir- 
cumferentially. 

Compensated  Alternator. — An  alternator  serving  to 
maintain  a  uniform  voltage  at  a  given  point  of  its 
circuit  under  differing  loads;  the  field  magnets  of 


ELECTRICAL  DICTIONARY  45 

which  are  called  into  activity  in  some  measure  by 
fixed  currents  taken  from  a  separate  generator  and 
to  some  extent  by  currents  furnished  by  the  load 
current  in  the  armature. 

Compensated  Voltmeter. — A  voltmeter  at  central  sta- 
tion connected  with  the  bus-bars  so  that  its  indica- 
tions are  corrected  automatically  for  the  pressure 
drop  in  some  certain  group  of  feeders  or  single 
feeder,  resulting  in  its  readings  corresponding  to 
the  pressure  furnished  to  the  mains. 

Compensated  Wattmeter. — A  wattmeter  wound  in  such 
manner  as  to  insure  compensation  for  the  effect  of 
reaction  in  a  shunt  circuit. 

Complement  of  Angle. — What  is  needed  to  make  the 
value  of  an  angle  equal  to  a  right  angle  or  90  de- 
grees. 

Complete  Wave. — Two  alternations  succeeding  each 
other  or  two  alternations  of  a  periodically  alter- 
nating quantity.  A  cycle. 

Component. — One  of  the  several  separate  forces  into 
which  any  one  force  can  be  resolved.  The  separate 
forces  which  united  produce  a  single  resulting 
force. 

Component  Currents. — The  currents  into  which  it  may 
be  apprehended  that  a  single  current  can  be  di- 
vided in  such  manner  as  to  become  the  equivalent 
of  the  single  current. 

Component  Electromotive  Forces. — The  two  or  more  E. 
M.  Fs.  into  which  any  given  E.  M.  P.  may  be  re- 
solved. 

Composite  Dynamo. — A  dynamo  of  compound  winding. 

Composite  Excitation. — Any  exciting  of  the  field  mag- 


46  ELECTRICAL  DICTIONARY 

nets  of  dynamos  in  which  there  has  been  used  more 
than  a  single  winding;  for  instance:  series  wind- 
ings and  shut  winding. 

Composite-Field  Dynamo. — A  dynamo  the  field  of  which 
has  a  composite  excitation,  or  is  compound  wound. 

Compound  Winding. — A  process  by  which  dynamos  and 
motors  are  wound  and  where  both  shunts  and  series 
coils  are  located  on  the  field  magnets. 

Compound-Wound  Continuous-Current  Generator. — A 
continuous  current  generator  the  fields  of  which 
are  compound  wound,  in  order  to  hold  the  pressure 
constant  under  all  loads. 

Compound- Wound  Motor. — A  motor,  the  field  of  which 
is  compound  wound,  in  order  to  keep  its  speed  con- 
stant under  all  loads. 

Concealed  Wiring. — Wiring  laid  in  the  plaster  in  the  in- 
terior of  structures  or  hidden  from  view  by  passing 
them  through  conduits. 

Condenser. — A  contrivance  for  augmenting  the  capac- 
ity of  an  insulated  conductor  by  placing  it  in  con- 
tiguity to  another  earth-connected  conductor,  but 
from  which  it  is  separated  by  any  intervening  body 
which  will  allow  electrostatic  induction  to  occur 
through  it. 

Conduct. — To  convey  electricity  through  conductors. 
To  be  able  to  carry  an  electric  current. 

Conducting  Power  for  Electricity. — The  capacity  of  a 
certain  length  and  area  of  a  regular  cross-section  : 
of  an  electric  conducting  material,  in  comparison 
with  that  possessed  by  the  same  length  and  area  of  | 
regular  cross-section  of  some  other  material  agreed 
upon  as  a  standard,  as  namely :  pure  copper. 


ELECTRICAL  DICTIONARY  47 

Conductivity,  Electric. — A  discharge  produced  by  car- 
rying the  charge  off  through  a  conductor  touching 
the  charged  body — the  opposite  of  a  convective  or 
disruptive  charge. 

Conductivity  Resistance. — The  resistance  to  an  electric 
conductor  made  by  a  body,  or  the  resistance  offered 
by  a  body  to  the  passage  of  electricity  through  its 
mass. 

Conductor. — Any  material  through  which  the  electric 
current  will  pass.  A  substance  which  has  the  power 
to  determine  the  direction  which  the  electric 
energy  will  take  in  passing  through  the  Ether  in 
the  dielectric  environing  it. 

Conduit,  Electric. — A  space  underground  in  which  is  a 
number  of  ducts  wherein  electric  wires  or  cables 
are  placed. 

Conduit  Trolley-System. — A  trolley  system,  single  or 
double,  whose  trolley  wires  are  laid  in  an  under- 
ground, slotted  conduit,  and  in  which  a  plow  or  sled 
pushed  or  drawn  through  the  slot  is  substituted  for 
the  trolley-wheel. 

Congelation. — The  process  of  passing,  or  the  act  of  con- 
verting from  a  fluid  to  a  solid  state  by  the  abstrac- 
tion of  heat.  Freezing. 

Connect. — To  effect  electric  contact. 

Connecting-up. — The  process  by  which  an  electric  cir- 
cuit is  made. 

Consequent  Pole. — A  magnet  pole  resulting  from  the 
placing  together  of  two  free  north  or  south  poles. 
A  magnet  pole  perfected  at  some  point  other  than 
the  extremities  of  a  magnet. 

Consonant  Electric  Circuit. — A  circuit  of  alternating 
current  having  inductance  and  resistance,  with  a 


48  ELECTRICAL  DICTIONARY 

secondary  current  having  capacity,  inductance  and 
resistance  in  such  way  as  to  cause  the  neutrali- 
zation of  the  inductance  of  the  primary  circuit  by 
the  inductance  and  capacity  of  the  secondary.  A 
primary  alternating-current  circuit  without  chok- 
ing effect  or  reactance,  due  to  the  presence  of  a  con- 
denser in  a  secondary  circuit,  in  distinction  from 
the  effect  of  a  condenser  introduced  directly  in  the 
primary  circuit. 

Constant  Current. — A  current  which  always  flows  in  the 
same  direction.  A  current  whose  strength  is  not 
subject  to  variation. 

Constant- Current  Arc-Lamp. — A  series  connected  arc- 
lamp. 

Constant-Current  Circuit. — A  circuit  the  current 
strength  of  which  remains  constant  despite  any 
changes  in  resistance. 

Constant-Current  Dynamo. — A  generator  with  constant 
current. 

Constant-Current  Transformer. — A  modification  in  the 
strength  of  a  constant  current. 

Constant-Potential  Arc-Lamp. — An  arc-lamp  used  on  in- 
candescent or  constant  potential  mains. 

Constant-Potential  Circuit. — A  circuit  the  potential  of 
which  is  maintained  nearly  constant. 

Constant-Potential  Dynamo. — A  dynamo  which  supplies 
a  nearly  constant  difference  of  potential  notwith- 
standing changes  of  resistance  or  load. 

Constant-Potential  Motor.— A  motor  intended  to  be 
worked  with  a  constant  potential  current.  Often  a 
motor  shunt  or  compound-wound. 


ELECTRICAL  DICTIONARY  49 

Consumer's  Terminals. — The  terminals  in  a  system  of 
electric  distribution  for  house  service  and  belong- 
ing to  the  house  and  at  which  the  supply  company 
delivers  the  electricity. 

Contact  Breaker. — A  device  employed  to  open  or  break 
an  electric  circuit. 

Contact  Resistance. — Resistance  resulting  at  the  point 
of  contact  of  several  surfaces. 

Contact  Screw. — A  screw  tipped  with  a  platinum  or 
other  contact  and  serving  to  close  the  circuit  of 
any  electric  device  in  the  circuit  of  which  it  is  situ- 
ated. 

Contacts. — Conducting  pieces  inserted  in  electric  cir- 
cuits with  a  view  to  open  and  close  the  circuit  at 
points  where  it  is  desirable.  A  fault  in  a  circuit 
resulting  from  any  part  of  the  circuit  coming  ac- 
cidentally in  contact  with  a  conducting  object.  A 
metallic  cross  or  back  connection  between  telephon- 
ic or  telegraphic  circuits. 

Continuous  Current. — An  electric  current  flowing  in  the 
same  direction  only. 

Continuous-Current  Arc. — A  voltaic  arc  effected  by  a 
continuous  current  and  differing  from  that  which 
results  from  alternating  currents. 

Continuous-Current  Generator. — A  generator  which  fur- 
nishes continuous  currents. 

Continuous-Current  Motor. — A  motor  worked  by  con- 
tinuous currents. 

Continuous-Current  Transformer. — A  dynamotor  or  mo- 
tor dynamo.  A  transformer  from  one  to  another 
continuous  pressure  and  current. 

Continuous-Surface  Commutator. — A  dynamo  com- 
mutator, the  gaps  of  which  instead  of  containing 


50  ELECTRICAL  DICTIONARY 

air  spaces,  are  filled  with  insulating  material;  or 
one  which  has  no  breaks  or  gaps  in  its  surface  be- 
tween adjacent  commutator  bars. 
Continuous  Winding. — A  term  often  used  to  designate 
wave  or  undulatory  winding  of  an  armature. 

Controller. — A  magnet,  whose  coils,  in  a  system  of  auto- 
matic constant  current  regulation,  are  crossed  by 
the  main  current  and  which  is  used  to  automatic- 
ally put  a  regulator  magnet  into  or  out  of  the  main 
current  on  changes  of  the  current  passing.  An 
electric  device  for  governing  a  circuit  or  system. 
An  electric  shunting  device  for  governing  the  speed 
of  motors.  A  controller  for  street  railroad  cars. 

Controller  Resistance. — The  resistance  used  with  street 
car  controllers  to  start  ^nd  stop  motors  or  for  mod- 
ifying their  speed. 

Controller  Switch. — The  switch  which  works  the  switch 
cylinder  on  a  street  car  controller. 

Converging  Magnetic  Flux. — Magnetic  flux  which  con- 
veys from  one  or  more  points. 

Conversion  of  Electromotive  Force. — Any  enhancement 
or  diminution  in  the  value  of  an  electro-motive 
force  obtained  by  the  employment  of  a  transformer. 

Convert. — To  modify  or  transform  an  electromotive  cur- 
rent. 

Converted  Currents. — Electric  currents  whose  strengths 
have  been  enhanced  or  diminished  by  use  of  a 
transformer. 

Converter. — A  term  applied  occasionally  to  a  trans- 
former. 

Convolutions  of  Wire. — The  individual  loops  or  turns 
in  a  coil. 


ELECTRICAL  DICTIONARY  51 

Cooling  Surface  of  Armature. — The  part  of  the  sur- 
face of  an  armature  from  which  it  radiates  into  the 
environing  atmosphere  the  heat  energy  in  it  which 
results  from  the  passage  of  the  currents  generated 
during  its  revolution. 

Co-Phasal. — Having  the  same  phases. 

Co-Phasal  Alternations. — Alternations  having  the  same 
phases. 

Copper  Bath. — An  electrolytic  bath  holding  in  electro- 
lyzable  solution  a  copper  salt,  and  a  plate  of  copper 
forming  the  anode  and  put  into  an  electrolyte  con- 
tiguous to  the  article  to  be  electro-plated  which 
constitutes  the  cathode. 

Copper  Conductivity  Standard. — A  metre-gramme  wire 
of  standard  conductivity  (in  accordance  with  the 
rules  of  the  British  Institution  of  Electrical  Engi- 
neers), with  a  resistance  of  0.1519  international 
ohm  at  15  degrees  C.,  agreeing  with  Matthiesen's 
standard  for  hard  copper. 

Copper  Efficiency. — The  relation  of  the  electric  power 
delivered  by  a  copper  system  to  the  power  de- 
livered to  that  system. 

Copper  Fuse-Wire  Terminals. — Copper  terminals  to 
which  the  terminals  of  fuse  wires  or  safety  catches 
are  connected. 

Copper  Loss. — The  loss  of  energy  sustained  by  the  cur- 
rent passing  through  the  copper  wire  of  a  motor, 
dynamo  or  any  conducting  system. 

Copper  Plating. — Plating  with  copper  by  the  electro 
plating  process. 

Copper  Ribbon. — A  style  of  copper  strap. 


52  ELECTRICAL  DICTIONARY 

Copper  Tape. — Copper  straps  or  bars  used  for  winding 
armatures. 

Copper-Zinc  Accumulator. — An  accumulator  formed  of 
a  copper  and  a  zinc  plate  immersed  in  a  solution  of 
sulphate  of  zinc. 

Coppered  Carbons. — Electrolytically  copper-coated  car- 
bons for  arc-lamps  or  batteries. 

Cord  Adjuster. — A  device  employed  to  regulate  the 
length  of  pendant  cords. 

Cord,  Electric. — An  electric  conductor,  flexible  and  in- 
sulated and  usually  containing  two  parallel  wires. 

Core  Discs. — Discs  cut  or  stamped  out  of  sheet  iron  and 
used  for  the  laminated  core  of  any  dynamo  electric 
apparatus. 

Core  Losses. — The  losses  sustained  by  the  core  of  a 
dynamo,  motor  or  transformer  resulting  from  hys- 
teresis or  eddy  currents.  The  Foucault  losses. 

Core  Losses  of  Transformer. — The  losses  in  the  core  of 
a  transformer  due  to  hysteresis  and  Faucault  cur- 
rents. Iron  losses  in  a  transformer. 

Core    Transformer. — A    transformer    where    the    wire 
windings  are  placed  on  the  core  of  iron  of  which  ] 
it  is  formed. 

Cored  Carbons. — Arc-light  carbons  having  a  soft  center 
of  carbon. 

Coreless  Armatures  of  Dynamo  or  Motor. — An  armature 
of  a  dynamo  or  motor  which  has  no  iron  core. 

Corpuscle. — A  minute  particle  or  physical  atom  which 
composes  large  bodies ;  not  the  elementary  prin- 
ciples of  matter,  but  small  simple  or  compound  par- 
ticles such  as  are  not  dissolved  or  dissipated  by 
heat. 


ELECTRICAL  DICTIONARY  53 

Cosine. — A  trigonometrical  function.     The  Sine  of  the 

complement  of  an  arc  of  an  angle. 
Cosine  Law  of  Illumination. — The  illuminative  intensity 

of  a  surface  illuminated  by  only  one  point  source, 

varies  as  the  cosine  of  the  angle  of  the  rays  incident 

upon  the  surface  from  that  source. 

Cotangent. — A  trigonometrical  function.  The  tangent 
of  the  complement  of  an  arc  or  angle. 

Coulomb. — The  unit  of  electric  quantity  accepted  for 
practical  use.  A  quantity  of  electricity  equal  to 
that  which  would  pass  in  one  second  through  a  cir- 
cuit conveying  one  ampere.  The  quantity  of  elec- 
tricity which  a  condenser  of  one  Farad  capacity 
contains  when  subjected  to  the  E.  M.  F.  of  one  volt. 

Coulomb  Meter. — A  meter  that  measures  in  coulombs 
the  quantity  of  electricity  passing  through  any  cir- 
cuit. 

Counter-Clockwise  Motion. — A  rotary  motion  which 
observed  when  facing  a  clock  is  opposed  in  its  di- 
rection to  that  of  the  clock's  hands. 

Counter-Electromotive  Force. — An  electromotive  force 
tending  to  send  out  a  current  in  the  opposite  direc- 
tion to  that  actually  emanating  from  a  source.  An 
electromotive  force  in  an  electric  motor  created  by 
the  revolution  of  the  armature  and  opposed  to  the 
force  generated  by  the  driving  current. 

Counter-Electromotive  Force  of  Arc. — An  electromotive 
force  created  while  a  carbon  voltaic  arc  is  forming 
and  opposed  to  that  which  sustains  the  arc. 

Counter-Electromotive  Force  or  Electrolysis. — A  coun- 
ter-electromotive force  resulting  from  electrolysis 
in  the  plating  bath  of  an  electrolytic  cell. 


54  ELECTRICAL  DICTIONARY 

Counter-Electromotive  Force  of  Mutual  Induction. — A 

counter-electromotive  force  created  by  reciprocal 
induction  between  adjacent  circuits. 

Counter  Pressure. — A  term  occasionally  applied  to 
counter-electromotive  force. 

Cradle  Dynamometer. — A  dynamometer  with  a  cradle 
which  holds  the  machine  to  be  tested,  and  the  me- 
chanical energy  which  it  takes  in  or  gives  out  is 
measured  by  the  torque  which  the  cradle  develops 
about  its  axis. 

Crater  in  Positive  Carbon. — A  cavity  in  the  end  of  a 
positive  carbon  of  an  arc  lamp  which  appears  after 
the  lamp  has  been  running  a  little  while. 

Creep  of  Belt. — A  term  applied  to  the  slipping  of  a  belt. 

Creeping  of  Voltaic  Cell. — The  deposit  or  incrustation 
due  to  the  efflorescence  of  salts  on  the  sides  of  the 
porous  cup  of  a  voltaic  cell,  or  on  the  binding  posts 
or  the  walls  of  the  container  holding  the  electrolyte. 

Creeping  of  Belt. — The' slipping  of  a  driving  belt  result- 
ing from  the  driving  pulley  traveling  faster  than 
the  driven  pulley. 

Creosoting. — A   process   employed  to   preserve   wood,. 

telegraph  poles,  etc.,  by  injecting  creosote  into  the 

pores  of  the  wood. 
Crevasse. — A  fine  split  in  a  magnetized  substance  used 

to  determine  the  magnetic  forces  on  a  small  needle. 

Critical  Pressure  of  a  Gas  or  Vapor. — The  lowest  point 
of  pressure  which  will  not  admit  of  the  vapori- 
zation of  a  substance  in  the  fluid  state  by  increase 
of  temperature;  but  where  instead,  it  changes  en- 
tirely into  gas.  The  lowest  point  of  pressure  where 
a  gaseous  substance  when  cooled,  liquefies  in  the 


ELECTRICAL   DICTIONARY 


55 


presence  of  its  vapor.  The  pressure  above  which  a 
gaseous  substance  will  not  liquefy,  however  much 
may  be  the  pressure. 

Critical  Temperature  of  a  Substance. — A  degree  of  tem- 
perature above  which  a  substance,  in  gaseous  form, 
will  not  liquefy,  however  much  pressure  may  be 
applied.  The  temperature  below  which  a  gaseous 
substance  is  subject  to  liquefaction  by  pressure,  it 
being  a  vapor. 

Crookes'  Effect. — An  effect  obtained  in  high  vacuum 
tubes,  resulting  from  motions  peculiar  to  heated  or 
electrified  molecules  when  in  high  state  of  radi- 
ation. 

Crookes'  Radiometer. — An  apparatus  which  demon- 
strates the  action  of  radiant  matter  in  effecting  mo- 
tion from  the  reactionary  effects  of  a  stream  of 
molecules  cast  off  from  a  number  of  unequally  heat- 
ed surfaces  which  are  easily  moved. 

Crookes'  Tubes. — Glass  tubes,  practically  total  vacuums 
employed  to  demonstrate  the  characteristics  of  the 
ultragaseous  condition  of  matter.  A  term  often 
applied  to  X-ray  tubes. 

Cross  Bonding. — The  bonding,  in  an  electric  railroad 
between  the  ground  feeder  and  the  track  employed, 
in  order  to  secure  a  good  conducting  return  circuit. 

Cross-Connected  Dynamo. — A  dynamo,  which  has  the 
ends  of  its  armature  coils  connected  to  correspond- 
ing segments  around  the  commutator. 

Cross  Current. — A  current  which  flows  between  the  ar- 
matures of  alternating  current  generators  worked 
in  parallel,  and  created  by  differences  in  magnitude 
or  phase  of  the  E.  M.  Fs.  in  the  machines. 


56  ELECTRICAL  DICTIONARY 

Cross,  Electric. — Usually  a  metallic  connection  occur- 
ring between  two  conducting  lines.  A  fault  in  any 
circuit  resulting  from  the  crossing  contact  of  two 
wires. 

Cross  System. — A  system  which  provides  for  the  run- 
.  ning  of  wires  overhead  in  order  to  prevent  recip- 
rocal inductive  perturbation,  and  which  is  effected 
by  the  crossing  or  transposition  of  the  wires  on  the 
pole  arms  at  desired  intervals,  in  contradistinction 
to  the  twist  system. 

Crow-Foot  Zinc. — A  zinc  like  a  crow's  foot  in  form  and 
used  in  the  gravity  voltaic  cell. 

Crucible,  Electric. — A  crucible  adapted  to  electro-metal- 
lurgical operations.  A  crucible  in  which  to  effect 
difficult  fusions  and  secure  the  separation  of 
metals  from  their  ores  or  to  form  alloys,  the  heat  of 
a  voltaic  arc  or  electric  incandescence  is  used. 

Crystal. — The  regular  form  which  a  substance  tends  to 
assume  in  solidifying  and  displaying  a  solid  body 
which  presents  symmetrically  arrayed  surfaces. 

Crystallization. — The  process  by  which  a  substance  in 
solidifying  through  solution  OF  fusion,  assumes  the 
form  of  a  crystal. 

Crystallize. — To  take  on  crystalline  form  in  the  separa- 
tion from  the  vaporous  or  liquid  condition. 

Cryptoscope. — An  apparatus  fashioned  in  form  of  a 
tube  of  pasteboard  having  a  florescent  screen  at 
one  end  and  which  is  viewed  through  an  eye-piece 
at  the  other  end. 

Cupric  Electrolysis. — Electrolysis  effected  in  electro- 
therapeutic  treatment,  by  copper  electrodes,  by 
which  means  a  salt  of  copper  is  conveyed  into  the 
tissues  under  the  anode  by  catophoric  action. 


ELECTRICAL   DICTIONARY  57 

Current  Density. — The  strength  of  current  which  flows 
in  any  part  of  a  circuit  divded  by  the  cross-section 
area  of  that  section  of  the  circuit. 

Current  Distribution. — The  branching  out  of  electric 
currents  through  a  conducting  or  ramified  mass. 

Current  Efficiency  of  Storage  Battery.— The  ratio  of  the 
whole  useful  electric  quantity  given  out  to  a  work- 
ing circuit  by  a  charged  storage  battery,  to  the 
whole  electric  quantity  used  to  charge  the  battery. 

Current  Electric. — The  quantity  of  electricity,  passing 
through  any  circuit,  per  second,  the  flow  being  uni- 
form. The  rate  attained  by  a  quantity  of  electric- 
ity in  passing  through  a  circuit.  The  relation  per 
second  considered  in  reference  to  electric  terms  of 
quantity,  between  the  electro-motive  force,  which 
causes  the  current,  and  the  opposing  resistance. 

Current  Strength. — The  quotient,  in  a  direct  current 
circuit  of  the  whole  electromotive  power,  divided 
by  the  whole  resistance.  The  time-measure  of  the 
flow  in  a  circuit  represented  by  amperes  or  cou- 
lombs per  second.  The  quotient  of  the  whole  electro- 
motive power,  in  an  alternating  circuit,  divided  by 
the  resistance. 

Current  Teaser,  Electric. — A  coil  of  fine  wire  used  OD 
the  field  magnets  of  an  electric  dynamo  or  motor, 
together  with  the  series  coils  already  wound  upon 
it,  and  which  is  connected  to  serve  as  a  shunt  across 
the  main  circuit. 

Current  Transformation. — The  changing  of  the  strength 
of  a  current  by  modifying  its  electro-motive  force. 
The  changing  of  a  direct  into  an  alternating  cur- 
rent, or  vice  versa,  or  the  changing  of  an  alternat- 
ing current  of  one  phase  into  a  current  of  many 
phases. 


58  ELECTRICAL  DICTIONARY 

Curve  of  Sines. — A  curve  which  represents  at  con- 
tinuous successive  positions  the  successive  values 
of  the  sines  of  a  progressively  varying  angle. 

Cut-Out. — To  abstract  an  electro-receptive  device  from 
the  circuit  of  an  electric  source. 

Cut-Out  Cabinet. — Any  enclosure  of  space  in  a  building 
arranged  for  the  reception  of  fuses  or  cut-outs. 

Cutting  Lines  of  Magnetic  Force. — The  cutting  or  in- 
tersecting of  lines  of  magnetic  force  or  flux  by  pass- 
ing a  conductor  through  such  lines  or  by  passing 
such  lines  through  a  conductor. 

Cycle. — Events  following  in  succession,  recurring  pe- 
riodically, the  reckoning  of  periodicity  being  taken 
from  any  moment  of  interruption  to  the  next  mo- 
ment of  occurrence. 

Cycle  of  Alternations. — The  cycle  of  an  electro-motive 
force,  current  or  flux,  alternating  periodically. 

Cyclometer. — An  instrument  which  records  the  number 
of  revolutions  made  by  a  wheel  or  any  other  re- 
volving device,  or  which  records  the  distance  cov- 
ered by  its  periphery. 

Cylindrical  Armature. — A  name  given  to  a  drum  arma- 
ture. 

Cylindrical  Core. — A  mass  of  iron,  cylindrical  in  form 
and  used  for  the  core  of  a  solenoid  or  helix.  A 
mass  of  soft  carbon,  cylindrical  in  form  and  used 
in  cored  electrodes. 


ELECTRICAL  DICTIONARY  '     59 


D. 

D.  C. — An  abbreviation  for  direct  current. 

D.  P.  Switch. — An  abbreviation  for  double  pole  switch. 

Damped  Galvanometer. — A  galvanometer  the  needle  or 

coil  of  which  comes  to  repose  almost  immediately 

when  moved. 

Damped  Vibrations. — Vibrations  occurring  under  con- 
ditions which  enable  the  swinging  or  oscillating 
motion  to  immediately  assume  repose  instead  of 
continuing  the  to  and  fro  movement  when  the  force 
which  causes  the  vibration  is  removed.  Vibrations 
of  successively  decreasing  amplitude. 

Damper. — A  metallic  cylinder  disposed  in  such  manner 
as  to  nearly  or  entirely  encompass  the  iron  core  of 
an  induction  coil  for  the  purpose  of  effecting  a 
variation  in  the  intensity  of  currents  produced  in 
the  secondary.  A  dash-pot  furnished  to  obviate 
the  too  sudden  movements  of  a  lever  or  other  mem- 
ber of  a  moving  contrivance. 

Damping. — The  stopping  of  sudden  oscillations  without 
waiting  their  cessation  after  reiterated  to  and  fro 
movements.  The  neutralization  of  the  motive 
energy  in  a  periodically  moving  body  by  the  ap- 
plication of  impeding  forces. 

Damping  Magnet. — Any  magnet  serving  to  check  the 
motions  of  a  moving  object  or  magnet. 

Dash-Pot. — A  cylinder  partly  filled  with  fluid  having 
a  loosely  fitting  piston  to  ease  the  blow  of  any  fall- 
ing weight.  A  contrivance  to  obviate  too  sudden 
motion  in  the  movable  members  of  an  apparatus. 


'60  ELECTRICAL  DICTIONARY 

Day  Load. — A  load  carried  on  a  machine  or  at  a  central 
station  during  the  day  time. 

Dead-Beat. — Damped  heavily.  That  motion  of  a  galva- 
nometer needle  which  describes  excited  movement 
from  point  to  point  and  returns  quickly  to  repose. 
Aperiodic. 

Dead-Beat  Galvanometer.  —  A  galvanometer  whose 
needle  does  not  reiterate  its  to  and  fro  oscillatory 
motion,  but  instead,  comes  quickly  to  repose. 

Dead  Ground  or  Grounding. — A  grounding  that  will 
secure  a  ground  of  negligible  resistance. 

Deci. — A  prefix  signifying  the  one-tenth  part. 

Deci-Ampere. — A  tenth  of  an  ampere. 

Deflection  of  Magnet. — The  deviation  of  a  magnetic 
needle  from  the  true  geographical  north. 

Declinometer. — An  instrument  for  measuring  the  decli- 
nation of  the  magnetic  needle. 

Decohere. — To  re-establish  or  recover  the  normal  con- 
dition of  a  coherer. 

Decomposition,  Electrolytic. — The  resolution  of  a  mole- 
cule into  its  composite  radicals  or  into  its  ultimate 
atoms  when  subjected  to  the  action  of  an  electric 
current. 

Deflection  of  Magnetic  Needle. — The  deviation  of  a 
needle  from  a  point  of  repose  either  in  the  earth's 
magnetic  field  or  in  that  of  another  magnet  and 
produced  by  the  influence  of  the  flux  of  an  electric 
-current  or  of  a  magnet. 

Deka. — A  prefix  expressing  ten  times. 

Deka-Ampere. — Ten  amperes. 

Deliquescence. — Liquefying  in  the  air.    The  solution  of 


ELECTRICAL  DICTIONARY  61 

a  crystalline  body  by  the  attraction  of  moisture 
from  the  atmosphere. 

Delivered  Power. — The  power  delivered  at  one  end  of 
a  line,  in  a  system  of  electrical  transmission,  in 
contradistinction  to  the  power  delivered  into  the 
line  at  the  other  end. 

Delta  Current. — In  a  triphase  system  the  current  be- 
tween contiguous  wires.  The  ring  current. 

Delta  Triphase-System. — A  triphase-system  with  ter- 
minal connection  similar  in  appearance  to  a  tri- 
angle or  the  Greek  letter  Delta. 

Demagnetization. — The  act  or  process  of  depriving  a 
magnet  of  magnetic  polarity. 

Demagnetization  by  Successive  Reversals. — The  act  of 
abstracting  the  magnetism  from  a  mass  of  magne- 
tized metal  by  exposing  it  to  the  action  of  succes- 
sive magneto-motive  forces,  which  alternate  in  di- 
rection and  are  gradually  reduced  to  zero. 

Density  of  Current. — The  quantity  of  current  which 
flows  per-unit-of-area  of  cross  section  in  any  section 
of  a  circuit. 

Density  of  Field. — The  quantity  of  magnetic  flux  which 
flows  through  any  field  per-unit-of-area  of  cross 
section. 

Depolarize. — To  deprive  of  polarity. 

Detector  Galvanometer. — Any  imperfected  pattern  of 
galvanometer  serving  to  detect  the  presence  of 
electric  currents. 

Diacritical  Current. — That  strength  of  a  magnetizing 
current  which  will  magnetize  an  iron  core  to  a  de- 
gree equal  to  one-half  saturation. 

Diacritical  Point  of  Magnetic  Saturation. — A  term  set 


62  ELECTRICAL  DICTIONARY 

forth  for  such  value  of  the  co-efficient  of  magnetic 
saturation  that  its  core  is  magnetized  precisely  to 
one-half  of  its  practicable  maximum  magnetization. 

Diamagnetic. — A  property  characterizing  zinc,  anti- 
mony, phosphorus,  bismuth  and  other  substances 
by  which  they  appear  to  be  repulsed  when  put  be- 
tween the  poles  of  strong  magnets. 

Diameter  of  Commutation. — The  diameter  at  that  part 
of  a  dynamo's  commutator  where  the  brushes 
touch.  The  diameter  of  the  commutator  of  an  open 
circuited  armature  which  is  in  direct  contact  with 
the  collecting  brushes. 

Diaphragm. — A  thin  plate  or  disc  of  elastic  material 
well  secured  at  its  edges  and  susceptible  to  vibra- 
tory motion.  The  porous  partition  of  an  endosmom- 
eter  or  of  a  voltaic  cell.  A  plate  with  a  circular 
opening  used  in  instruments  to  cut  off  marginal 
portions  of  a  beam  of  light  as  at  the  focus  of  a 
telescope. 

Diaphragm  Photometer. — A  photometer  whose  func- 
tional operation  is  dependent  upon  the  equality  of 
the  effulgence  produced  on  the  two  halves  of  a 
diaphragm  by  altering  the  distances  of  the  light 
effects  from  the  diaphragm,  or  by  changing  the 
inclination  of  the  bright  rays  on  it. 

Dielectric. — Any  substance  through  whose  mass  elec- 
trostatic induction  is  allowed  to  occur. 

Dielectric  Hysteresis. — A  kind  of  molecular  friction  cor- 
responding  to  hysteresis  occurring  in  a  dielectric 
under  changes  of  electrostatic  stress.  A  certain 
property  of  a  dielectric  which  permits  the  consump- 
tion of  energy  in  reversals  of  electrification. 


ELECTRICAL  DICTIONARY 


63 


Dielectric  Hysteretic  Impedance. — The  apparent  com- 
ponent of  resistance  or  obstruction  in  an  alternat- 
ing current  circuit  resulting  from  dielectric  hys- 
teresis. 

Dielectric  Hysteretic  Lag. — In  an  alternating  current 
circuit  the  lag  resulting  from  dielectric  hysteresis. 

Difference  of  Potential. — That  property  in  space  relat- 
ing to  quantity,  by  which  work  is  performed  when 
a  mass  of  matter  is  shifted  from  one  point  to  an- 
other. 

Difference  of  Magnetic  Potential. — That  property  in 
space  relating  to  quantity,  by  which  work  is  per- 
formed when  a  magnetic  pole  moves  in  it.  The 
magnetic  performance  on  a  unit  magnetic  pole  in 
a  trip  between  two  points. 

Difference  of  Thermal  Pressure. — A  phase  used  at  times 
for  the  variation  of  temperature  existing  between 
two  points  in  a  conducting  material  which  is  sup- 
posed to  produce  the  flow  of  heat  from  the  higher 
to  the  lower  temperature,  through  such  conductor. 

Differential  Compound  Motor. — A  compound  motor 
wherein  the  magneto-motive  force  of  the  working 
current  operates  in  opposition  to  a  like  force  of  the 
shunt  excitation  in  order  to  keep  the  speed  con- 
stant under  all  loads. 

Differential  Electric  Arc-Lamp. — A  term  used  signify- 
ing a  derived  circuit  arc-lamp,  the  lighting  magnet 
of  which  consists  of  a  core  with  series  of  shunt 
coils  or  of  two  individual  cores  opposed  to  each 
other,  one  containing  the  shunt  winding  and  the 
other  the  series. 

Differential  Electro-Magnet. — An  electro-magnet  dif- 
ferentially wound. 


64  ELECTRICAL  DICTIONARY 

Differential  Permeability. — In  a  substance  being  sub- 
jected to  magnetization,  the  differential  co-efficient 
of  flux  density  to  the  magnetizing  force. 

Differential  Winding. — A  manner  of  double  winding 
of  magnet  coils  which  results  in  the  opposition  of 
the  two  poles  to  each  other. 

Differential  Winding  of  Field. — A  manner  of  field  mag- 
net winding  resulting  in  two  exciting  currents 
exerting  opposing  magneto-motive  forces.  A  man- 
ner of  winding  which  results  in  the  magnetizing 
flux  of  the  series  coil  being  opposed  by  that  of  the 
shunt  coil. 

Differentially  Wound  Motor.  —  A  motor  compound 
wound  wherein  the  shunt  coil  current  opposes  in 
its  magnetizing  consequence,  the  current  in  the 
series  coil,  so  that  the  difference  between  the  mag- 
netizing effects  of  the  two  coils  is  equal  to  the 
efficient  magnetizing  effect  produced. 

Diffusion  of  Magnetic  Flux. — The  lateral  deviation  of 

magnetic  flux  from  the  direct  course  between  the 

poles  which  produce  it. 
Dimensions  of  Units. — The  exponential  values  tacitly 

assigned  to  units  of  length,  time  and  mass. 
Dimmer. — A  choking  coil  used  in  an  alternating  current 

system  of  distribution  for  governing  the  strength 

of  current   flowing   through   incandescent   lamps. 

Resistance   used   to    reduce    the    flow    of   current 

through  incandescent  lamps. 

Dioptrics. — The  science  which  treats  of  the  laws  of  the 

refraction  of  light. 
Dip. — Dip  of  the  needle  or  magnetic  dip.    The  inclina- 

tidn  of  the  magnetic  needle. 


ELECTRICAL  DICTIONARY  65 

Diphase-Alternating  Currents. — Two  individual  alter- 
nating electric  currents  with  a  phase  difference  of 
one-quarter  of  a  cycle.  Two-phase  currents.  Quar- 
ter-phase currents. 

Diphase  Rotary  Field. — A  magnetic  field  obtained  by 
the  employment  of  four  or  more  magnet  poles 
wound  in  such  manner  as  to  require  their  polarity 
to  alternate  with  changes  in  the  direction  of  the 
current,  and  in  addition,  to  act  as  though  the  field 
rotated.  A  rotating  magnetic  field  effected  by  di- 
phase  currents. 

Diplex  Telegraphy. — A  method  providing  for  the  trans- 
mission of  two  telegraphic  messages  over  a  single 
wire  and  in  the  same  direction  simultaneously. 

Diplex  Telephony. — A  method  providing  for  the  trans- 
mission of  two  telephonic  messages  simultaneously 
in  the  same  direction  and  over  the  same  wire. 

Dipping. — An  electro-metallurgical  process  in  which  a 
metallic  salt  is  dipped  in  a  solution  of  resolvable 
metallic  salt  whereby  a  light  deposit  or  plating  of 
metal  is  obtained  on  its  surface.  Preparing  sur- 
faces for  electro-plating  by  dipping  them  in  cer- 
tain acid  fluids. 

Dipping  Basket. — A  non-corrosive  perforated  basket 
used  in  electro-plating  to  hold  articles  which  are 
to  be  dipped  in  the  cleaning  solution. 

Dipping  Hook. — A  metallic  hook  used  in  electro-plating 
to  hold  the  articles  which  are  to  be  dipped  in  the 
cleansing  solution. 

Dipping  Magnetic-Needle. — A  magnetic  needle  so  sus- 
pended as  to  be  free  only  in  a  vertical  plane  and 
used  to  ascertain  the  magnetic  inclination. 


56  ELECTRICAL  DICTIONARY 

Direct-Coupled  Dynamo. — A  dynamo  the  shaft  of  whose 
armature  is  coupled  directly  to  the  driving  shaft. 

Direct-Current  Dynamo-Electric  Machine. — A  dynamo- 
electric  machine  which  has  the  capacity  to  supply 
direct  currents. 

Direct-Current  Electric  Motor.  —  An  electric  motor 
which  is  driven  by  direct  currents  in  contr-a-dis- 
tinction  to  one  driven  by  alternating  currents. 

Direct-Current  Rotary  Transformer. — A  term  applied 
to  a  rotating  secondary  generator  of  continuous 
currents. 

Direct  Reading  Galvanometer. — A  galvanometer  having 
the  absolute  value  of  the  deflection  and  current 
strength  directly  indicated  instead  of  reckoned. 

Direction  of  Electric  Current. — An  assumption  that  an 
electric  current  leaves  its  source  at  its  positive  pole 
and  re-enters  it  at  its  negative  pole. 

Direction  of  Lines  of  Force. — The  direction  of  magnetic 
flux. 

Direction  of  Magnetic  Flux. — An  assumption  that  mag- 
netic flux  leaves  a  magnet  at  its  north-seeking  pole 
and  re-enters  it  at  its  south-seeking  pole. 

Disc  Armature. — An  armature  of  a  dynamo  electric 
machine  the  windings  of  which  are  composed  of 
flat  coils  maintained  on  the  surface  of  a  disc. 

Discharge. — The  equalization  of  differences  of  potential 
by  connecting  them  by  a  conductor.  To  equalize 
the  difference  of  potential  between  the  terminals 
of  a  condenser  by  connecting  them  with  a  conduc- 
tor. The  abstraction  of  a  charge  from  a  conductor 
by  connecting  it  to  the  earth  or  another  conductor. 
The  abstraction  of  a  charge  from  an  insulated  con- 


ELECTRICAL  DICTIONARY  67 

ductor  by  the  use  of  a  current  of  electrified  air 
atoms. 

Disconnect. — To  break  an  electric  circuit  or  open  it. 
To  abstract  an  electro-receptive  contrivance  from 
a  circuit. 

Disconnection. — A  term  used  generally  to  indicate 
divers  faults  occasioned  by  a  circuit  accidentally 
breaking  or  becoming  disconnected.  The  pur- 
posely opening  or  breaking  of  a  circuit  or  the  ab- 
straction from  it  of  an  electro-receptive  contriv- 
ance. An  interruption  in  the  continuity  of  a  cir- 
cuit. 

Disintegration  of  Storage  Battery  Plate. — The  gradual 
wearing  and  falling  away  of  the  live  material  of 
a  storage  battery  plate  from  the  perforations  of  the 
grid. 

Dissipation  Function. — A  function  signifying  the  rate 
at  which  the  passage  of  an  electric  current  through 
a  conductor  produces  heat. 

Dissipation  of  Energy. — The  scattering,  loss  or  waste 
of  usable  energy. 

Dissonance,  Electric. — Electrical  discord.  A  term  ap- 
plied to  alternating  electro-motive  forces  with  op- 
posed phases,  and  signifying  the  opposite  of  elec- 
tric consonance. 

Distillation,  Electric. — The  distilling  of  a  liquid  by  the 
employment  of  electricity  which,  by  electrifying 
the  liquid,  assists  the  effects  of  the  heat. 

Distorsion. — The  state  of  being  wrested  or  twisted  out 
of  natural  shape  or  position  produced  in  an  entity 
by  the  action  of  a  'stress. 


68  ELECTRICAL  DICTIONARY 

Distorsion  of  Magnetic  Field. — An  alteration  in  the 
direction  and  dispensation  of  the  magnetic  flux  in 
the  field  of  a  dynamo  armature,  effected  by  the 
magneto-motive  power  of  the  armature  current. 

Distributing  Board. — A  term  given  to  a  cross  connect- 
ing board  in  a  telephonic  or  telegraphic  system. 
A  board  which  is  the  terminating  point  for  the 
wires  from  a  telephone  switchboard  and  where  con- 
nection with  the  circuit  wires  is  effected.  An  in- 
sulating board  equipped  with  screw-connecting 
pieces  and  serving  in  a  distributing  'system  to  con- 
nect branch  circuits  to  mains,  with  or  without  fuse 
cut-outs. 

Distributing  Box. — A  box  so  equipped  as  to  be  easily 
able  to  change  the  connections  of  distributing  cir- 
cuits with  the  source  from  which  they  receive  their 
supply.  A  box  located  at  a  point  of  distribution 
and  containing  the  fuses  appertaining  to  that  sec- 
tion of  the  distributing  system. 

Distributing  Mains. — The  mains  used  in  a  feeder  system 
of  parallel  conductors. 

Distributing  Center. — A  point  of  ramification.  The 
center  of  distribution  in  a  distributing  system. 

Distribution  of  Electricity  by  Commutating  Transform, 
ers. — A  system  of  distribution  employing  motor 
generators  whose  field  magnets  and  armatures  do 
not  revolve  as  a  special  commutator  is  used  to 
charge  the  polarity  of  the  magnetic  circuit. 

Distribution  of  Electricity  by  Means  of  Transformers. — 
A  system  whereby  the  electric  energy  is  conveyed 
by  means  of  continuous  currents  which  are  trans- 
mitted over  the  line  to  conveniently  located  stations 
at  which  motor  dynamos  do  duty  for  transformers. 


ELECTRICAL  DICTIONARY 

Distribution  of  Electricity   by  Motor   Generators. — A 

system  of  electric  distribution  wherein  an  uninter- 
rupted electric  stream  of  high  potentiality,  dis- 
tributed through  the  main  line,  is  employed  at  the 
place  where  its  energy  is  to  be  made  use  of,  to  drive 
a  motor,  which  drives  a  dynamo,  the  current  of 
which  serves  to  energize  the  electro-receptive  de- 
vices. 

Diurnal  Load-Factor. — The  ratio  between  the  whole 
number  of  units  delivered  from  a  station  during 
twenty-four  hours  to  the  number  which  would 
have  been  delivered  had  the  work  of  the  plant  been 
performed  under  its  maximum  load  during  that 
time. 

Divergent  Flux. — A  flux  whose  intensity  diminishes  by 
divergence  or  diffusion  as  it  proceeds  along  its 
course. 

Door-Opener,  Electric. — An  electro-magnetic  contriv- 
ance used  to  open  a  door  from  a  distance. 

Door  Push. — A  contact,  as  in  a  burglar  alarm  system, 
which  opens  or  closes  by  the  opening  or  closing  of 
a  door  or  window  and  sounds  the  alarm  from  a 
distance. 

Double-Armature  Windings. — Two  armature  windings 
fixed  to  a  core  symmetrically,  with  their  respec- 
tive ends  connected  to  alternate  commutator  bars. 

Double-Balance  Relay. — Two  relays,  in  a  closed  current 
telegraph  alarm  system,  which  are  connected  in 
series,  one  serving  to  close  a  local  circuit  in  the 
event  the  main  line  current  weakens  noticeably, 
and  the  other  serving  to  close  a  local  circuit  if  the 
main  line  current  should  strengthen  noticeably. 


70  ELECTRICAL  DICTIONARY 

Double-Break  Switch. — A  two-pole  switch.  A  switch 
serving  to  break  a  circuit  at  two  points  in  which 
it  is  distinguished  from  a  switch  which  breaks  a 
circuit  at  only  one  place. 

Double-Carbon  Arc-Lamp. — An  arc-lamp  provided  with 
two  sets  of  carbon  electrodes  which  enable  it  to 
burn  all  night  without  being  replenished  with 
other  carbons;  the  two  sets  being  so  disposed  that 
when  one  set  burns  out  the  current  is  switched 
automatically  to  the  other  set. 

Double-Contact  Push. — A  push  having  two  contacts  and 
so  contrived  that  pressure  upon  it  opens  one  con- 
tact and  closes  the  other. 

Double-Deck  Switchboard. — A  switchboard  having  two 
rows  of  switches  and  instruments,  one  over  the 
other. 

Double-Filament  Lamp. — An  incandescent  lamp  often 
used  as  a  side  light  for  a  vessel,  and  supplied  with 
two  carbon  filaments,  adjusted  so  that  in  case  one 
should  break,  the  other  will  continue  to  burn.  An 
incandescent  lamp  requiring  double  the  pressure 
of  an  ordinary  lamp  by  reason  of  its  having  two 
filaments  connected  in  series. 

Double-Pole  Cut-Out. — A  cut-out  which,  by  a  single 
action,  cuts  out  both  the  positive  and  the  negative 
leads.  Two  safety  fuses  occupying  the  same  holder 
and  being  respectively  connected  to  the  positive 
main  and  negative  main. 

Double-Pole  Switch. — A  switch  serving  to  break  the 
circuit  -of  both  the  positive  and  negative  leads  at 
the  same  instant. 

Double-Reduction. — A  velocity  reducer  for  gear  wheels 


ELECTRICAL  DICTIONARY  71 

using  two  gear  wheels  and  two  pinions,  or  one  in- 
termediate shaft. 

Double-Reduction  Car-Motor. — A  car-motor  equipped 
with  a  double  reduction  or  an  intermediate  gear 
shaft  between  the  car  wheel  and  motor  shaft. 

Double-Throw  Switch. — A  switch  which  can  be  thrown 
into  either  one  of  two  contacts.  A  throw-over 
switch. 

Double-Trolley. — In  a  double  over-head  system,  two  dis- 
tinct trolleys  carried  on  the  same  car  and  running 
over  two  distinct  wires  which  make  a  metallic  cir- 
cuit. 

Double-Truck  Car. — A  car  resting  on  two  separate 
single  trucks,  a  plan  adopted  for  long  cars  to  in- 
sure safety  and  convenience  in  turning  short 
curves. 

Double- Winding  of  Armature. — An  armature  winding 
supplied  with  two  distinct  windings  or  sets  of  coils* 
the  windings  being  insulated  from  each  other  and 
connected  to  the  commutator  at  every  other  seg- 
ment, providing  thus  for  the  brushes  to  repose 
upon  corresponding  segments,  connected  with  each 
winding,  and  thereby  allowing  each  winding  to 
supply  one-half  the  current  strength  with  an  ac- 
companying diminution  in  the  inductance  of  each 
circuit. 

Double- Wire  Moulding. — A  moulding  providing  for  the 
accommodation  of  two  wires  each  in  a  distinct 
groove. 

Drag  of  Magnetic  Field. — A  term  applied  at  times  to 
the  torque  or  electro-dynamic  force  resulting  from 
the  presence  of  an  active  conductor  in  a  magnetic 
field, 


72  ELECTRICAL  DICTIONARY 

Draw-Bar. — The  bar  which  connects  a  locomotive  with 

its  train. 
Draw-Bar  Pull. — The  pull  exerted  by  a  locomotive  at 

its  draw-bar  as  discriminated  from  its  motor  pull. 

Driven  Pulley. — A  pulley  to  which  the  motion  is  given 
by  a  driving  shaft. 

Driven  Shaft. — A  shaft  operated  by  a  driving  pulley 

belt. 
Driving  Pulley. — The  pulley  of  a  machine  located  on 

the  driving  shaft. 

Driving  Pulley  of  Motor. — A  pulley  mounted  on  the 
shaft  of  a  motor  or  a  pulley  which  conveys  the 
mechanical  power  of  a  motor. 

Driving  Shaft. — A  shaft  connected  immediately  with 
a  prime  mover. 

Drop. — A  word  signifying  the  drop  of  potential,  pres- 
sure or  electro-motive  force.  The  fall  of  potential 
occurring  in  an  active  conductor,  due  to  its  resist- 
ance. 

Drop  Annunciator. — An  electro-magnetic  annunciator 
which,  when  energized,  sets  free  a  shutter  and 
allows  it  to  drop. 

Drop  of  Potential. — The  decrease  of  potential  equal  in 
any  section  of  a  circuit  to  the  product  of  the  re- 
sistance and  the  current  strength  in  that  section 
of  the  circuit. 

Drop  of  Voltage. — The  difference  of  potential  of  any 
section  of  a  circuit. 

Drum  Armature. — A  dynamo  armature  with  coils 
wound  over  the  exterior  part  of  a  drum  in  the  di- 
rection of  its  length. 


ELECTRICAL  DICTIONARY  73 

Dry  Battery. — Several  distinct  dry  voltaic  cells  con- 
nected in  a  manner  to  act  as  a  single  source. 

Dry  Transformer. — A  transformer  air-insulated;  being 
thus  distinguished  from  an  oil-insulated  trans- 
former. 

Duct. — A  space  in  a  conduit  underground  for  a  single 
wire  or  cable. 

Dummy  Moulding. — An  ornamental  moulding,  not  in- 
tended to  receive  a  wire ;  but  placed  on  the  ceiling 
to  preserve  the  symmetry  of  the  decorative  ar- 
rangement which  includes  the  useful  mouldings 
into  which  wires  are  laid. 

Duplex  Cable. — A  cable  consisting  of  two  separate  con- 
ductors paralleling  each  other. 

Duplex  Telegraphy. — A  system  providing  for  the  trans- 
mission of  two  telegraphic  messages  over  a  single 
wire  simultaneously  in  opposite  directions. 

Duplex  Transmission. — The  transmission  of  two  tele- 
graphic or  telephonic  messages  simultaneously  over 
the  same  wire  in  opposite  directions. 

Duplex  Wire. — An  insulated  conductor  having  two  dis- 
tinct parallel  wires. 

Dust  Telephone-Transmitter. — A  style  of  microphone 
transmitter  supplied  with  a  carbon  dust  contained 
in  a  conveniently  arranged  box  which  is  connected 
with  the  transmitter's  terminals. 

Dynamic  Electricity. — A  term  applied  to  current  elec- 
tricity as  distinguished  from  static  electricity. 

Dynamics. — That  branch  of  mechanics  which  treats  of 
the  action  of  forces  producing  motion  in  bodies. 

Dynamo. — A  dynamo  electric  machine.    A  generator. 


74  ELECTRICAL  DICTIONARY 

Dynamo  Brush-Holder. — Contrivances  for  holding  the 
collecting  brushes  of  dynamo  electric  machines. 

Dynamo-Electric  Machine. — A  machine  which,  by 
means  of  electro-dynamic  induction,  converts  me- 
chanical energy  into  electric  energy.  A  dynamo. 

Dynamo  or  Motor  Frame. — The  iron  frame  of  a  dynamo 
or  motor  with  the  standards  and  pole  pieces  in- 
cluded, but  not  the  bearings  and  base  plates. 

Dynamo  Regulator. — A  term  applied  to  a  style  of  rheo- 
stat used  in  regulating  a  dynamo. 

Dynamo  Resistance  Box. — A  style  of  rheostat  used  for 
regulating  a  dynamo. 

Dynamo  Terminals. — A  dynamo 's  main  terminals. 

Dynamometer. — An  instrument  for  measuring  force  or 
power. 

Dyne. — The  C.  G.  S.  unit  of  force.  The  force  capable 
of  imparting  in  one  second  a  velocity  of  one  centi- 
meter per  second  to  a  mass  of  one  gramme. 


E.  H.  P. — An  abbreviation  of  Electrical  horse  power. 

E.  M.  F. — An  abbreviation  of  Electro-motive  force. 

Ear  Piece. — A  round  opening  into  an  air  chamber  super- 
posing the  diaphragm  of  a  telephone  receiver  and 
so  shaped  as  to  conveniently  fit  the  ear. 

Earth. — A  defect  in  any  line  of  electric  conduction  re- 
sulting from  accidental  contact  of  such  line  with 
the  earth  or  ground.  That  earth  or  ground  which 
forms  part  of  an  electric  circuit. 


ELECTRICAL  DICTIONARY  75 

Earth  Circuit. — A  circuit,  the  course  of  which,  is  formed 
partly  by  the  earth  or  ground.  A  part  of  the 
ground  or  earth  with  which  an  electric  circuit  has 
been  established. 

Earth  Connection. — A  connection  which  is  formed  by 
a  conductor  connected  to  any  circuit  or  apparatus 
and  the  ground. 

Earthenware  Conduit. — A  glazed  earthenware  conduit 
usually  containing  many  ducts. 

Earth-Grounded  Wire. — A  wire  having  one  of  its  ter- 
minals placed  in  the  ground,  the  earth  thereby 
forming  a  part  of  the  circuit. 

Earth  Plates. — Metallic  plates  sunk  in  the  ground  or  in 
water  to  which  the  terminals  of  earth  wires  are 
connected. 

Earth  Return. — A  section  of  a  grounded  circuit  the  con- 
ducting course  of  which  is  formed  by  the  earth. 

Ebonite. — A  material  composed  of  india-rubber  and  sul- 
phur, very  hard,  highly  insulating  and  possessing 
specific  inductive  properties  to  a  high  degree. 

Economic  Coefficient. — The  relation  between  the  total 
delivery  of  a  dynamo  and  the  total  electric  power 
actually  converted  in  the  machine. 

Economic  Coefficient  of  Dynamo-Electric  Machine.— 
The  relation  of  the  electric  force  which  a  dynamo 
produces  at  its  terminals  to  the  mechanical  power 
employed  to  drive  it. 

Eddy  Currents. — Useless  currents  in  the  armature,  pole 
pieces  and  magnetic  cores  of  dynamos  or  other 
masses  of  metal,  created  by  the  varying  strength 
of  contiguous  electric  currents,  or  by  their  motion 
through  magnetic  flux. 


,    76  ELECTRICAL  DICTIONARY 

Edison  Distributing-Box. — A  box  used  in  the  three  wire 
Edison  distribution  system. 

Edison-Lalande  Cell. — A  zinc-copper  couple  having  a 
depolarized  coating  of  copper-oxide  on  the  copper, 
the  couple  being  immersed  in  an  electrolyte  of  pot- 
ash or  caustic  soda. 

Effective  Starting-Current  of  Motor.— The  value  of  the 
initial  current  of  a  motor  indicated  by  an  ammeter. 

Efficiency.— The  relation  of  a  result  effected  to  the  ex- 
penditure necessary  to  effect  the  result. 

Efficiency  of  Conversion  of  Dynamo. — The  whole  sum 
of  electric  energy  produced  by  a  dynamo  divided 
by  the  sum  total  of  the  mechanical  energy  nec- 
essary to  drive  it. 

Efficiency  of  Electric  Lamp.— The  relation  of  the  lumi- 
nous energy  given  out  by  an  incandescent  lamp  to 
the  energy  which  it  absorbs.  The  relation  of  the 
number  of  candles  to  be  had  from  an  electric 
lamp  to  its  electric  activity  indicated  in  watts. 

Efficiency  of  Electric  Motor. — The  relation  of  the  elec- 
tric power  discharged  at  a 'motor  pulley  to  that 
which  is  furnished  at  its  terminals. 

Efficiency  of  Transformer  or  Converter. — The  relation 
of  the  electric  power  furnished  at  a  transformer's 
secondary  terminals  to  that  furnished  at  its  pri- 
mary terminals. 

Efflorescence. — A  change  of  crystalline  salts  to  a  powder 
from  gradual  decomposition  upon  exposure  to  air, 
due  to  loss  of  the  crystallization  water. 

Elasticity. — A  property  inherent  in  bodies  by  which 
they  recover  their  former  figure  or  dimensions  upon 
the  removal  of  external  pressure  or  stress. 


ELECTRICAL  DICTIONARY  77 

Electric. — Pertaining  to  electricity. 
Electrically. — By  means  of  electricity. 
Electrician. — A  person  versed  in  the  science  and  appli- 
cation of  electricity. 

Electricity. — A  term  applied  to  that  unknown  power  in 
nature  which  produces  electric  phenomena. 

Electro-Bath. — The  liquid  solution  used  in  electro- 
plating. 

Electro-Brassing. — Depositing  brass  upon  a  surface  by 
electrolysis  or  electro-plating. 

Electro-Capillary  Phenomena. — An  electric  appearance 
noticeable  in  capillary  tubes  where  the  surfaces  of 
two  liquids  come  in  contact. 

Electro-Chemical. — Pertaining  to  electro-chemistry. 
Electro-Chemical  Decomposition. — Electrolysis    or    de- 
composition by  means  of  electricity. 

Electro-Chemist. — A  person  well  versed  in  the  science 
of  electro-chemistry. 

Electro-Chemistry. — The  department  of  electric  science 
which  treats  of  combinations  and  decompositions 
produced  by  the  electric  current. 

Electro-Coppering-. — Coating  a  surface  with  copper  by 
the  electro-plating  process. 

Electro-Deposit. — A  layer  of  metal  deposited  upon  an 
article  by  electro-plating. 

Electro-Deposition. — The  act  of  coating  with  metal  by 
electrolysis. 

Electro-Dynamic  Machinery. — Any  machinery  serving 
to  produce,  transmit,  measure  or  use  energy  by 
means  of  electricity. 


78  ELECTRICAL  DICTIONARY 

Electro-Dynamic  Motor. — An  electric  motor  or  one  ope- 
rated by  means  of  electro-dynamic  force. 

Electro-Dynamic  Rotation. — Rotation  produced  by 
electro-dynamic  force. 

Electro-Dynamics. — The  branch  of  electric  science  treat- 
ing of  the  action  upon  one  another  of  electric  cur- 
rents, or  their  action  upon  themselves  or  upon 
magnets. 

Electro-Etching. — A  term  applied  to  engraving  by  elec- 
tricity. 

Electro-Extraction  of  Ores. — Divers  processes  by  which 
metals  are  electrically  extracted  from  ores. 

Electro-Kinetic  Energy. — Electrical  energy  in  actual 
performance  of  work. 

Electro-Kinetics. — A  term  given  to  the  appearances  of 
electricity  in  motion  or  currents  of  electricity;  in 
contrast  to  electrostatics  or  of  the  appearances  of 
electric  charges  or  electricity  in  repose. 

Electro-Magnet. — A  magnet  obtained  by  the  flow  of  an 
electric  current  through  an  insulated  wire  circuit. 
A  coil  possessing  magnetizing  power  encompassing 
a  soft  iron  core  which  is  susceptible  to  instant  mag- 
netization or  demagnetization  when  the  circuit  is 
opened  or  closed. 

Electro-Magnetic  Ammeter. — A  style  of  ammeter  whose 
needle  is  moved  in  oppostion  to  the  field  of  an 
electro-magnet  by  the  field  of  the  current  it  is 
measuring. 

Electro-Magnetic  Attraction. — The  reciprocal  attraction 
of  the  unlike  poles  of  electro-magnets. 

Electro-Magnetic  Bell. — A  bell  set  in  motion  electro- 
magnetically. 


ELECTRICAL  DICTIONARY  79 

Electro-Magnetic  Brake. — A  car-wheel  brake  either  de- 
riving its  power  from  electro-magnetism,  or  which 
is  operated  by  electro-magnetic  contrivances. 

Electro-Magnetic  Cut-Out. — A  cut-out  which  acts  by  the 
use  of  an  electro-magnet. 

Electro-Magnetic  Field. — That  field  which  either  an 
electric  current  or  an  electro-magnet  produces. 

Electro-Magnetic  Flux. — Magnetic  flux  created  by  ?t» 
electric  current  or  electro-magnetism. 

Electro-Magnetic  Helix. — An  electro-magnetic  solenoid 

Electro-Magnetic  Induction. — A  kind  of  electro-dy- 
namic induction  wherein  by  the  motion,  either  of 
electro-magnets  or  electro-magnetic  solenoids,  elec- 
tric currents  are  obtained. 

Electro-Magnetic  Inertia. — A  term  applied  to  the  self- 
inductance  of  a  current. 

Electro-Magnetic  Rotation. — Rotation  resulting  from 
electro-magnetic  attractions  and  repulsions,  as  in 
a  motor. 

Electro-Magnetic  Separator. — A  contrivance  by  which 
the  dross  is  separated  from  the  ore  of  finely  pow- 
dered low-grade  iron  ores.  A  contrivance  provid- 
ing for  the  elimination  of  particles  of  iron  from 
non-magnetic  filings  by  magnetic  attraction. 

Electro-Magnetic  Solenoid. — A  coil  of  wire,  cylindrical 
in  form,  each  of  its  convolutions  being  circular. 
An  electro-magnetic  helix. 

Electro-Magnetic  Temperature-Regulator. — An  instru- 
ment for  registering  temperature  electro-magneti- 
cally.  A  regulator  of  temperature  whose  perform- 
ance is  contingent  upon  the  operation  of  an  electro- 
magnet, whose  action  is  excited  by  the  expansion 
or  contraction  of  a  solid  or  fluid. 


80  ELECTRICAL  DICTIONARY 

Electro-Magnetism. — Magnetism  created  by  electric 
currents. 

Electro-Mechanical  Bell. — A  bell  moved  to  action  by  the 
force  exerted  upon  its  striking  mechanism  by  an 
electro-magnet. 

Electro-Mechanical  Gong. — A  gong  whose  operation  de- 
pends upon  the  action,  at  times,  of  an  electric 
current  upon  its  striking  mechanism ;  the  blow  be- 
ing struck  by  mechanical  force. 

Electro-Metallurgical  Galvanization. — A  process  for  de- 
positing a  light  metallic  coating  by  electrolytic 
deposition  upon  the  surface  of  any  conductor,  such 
as,  for  instance :  the  carbon  electrodes  employed  in 
arc  lamps. 

Electro-Metallurgy. — The  department  of  electric  science 
which  pertains  to  the  reduction  or  treatment  of 
metals  by  electricity. 

Electro-Percussion  Drill. — A  drill  used  in  mining  or 
excavating  rock  and  which  operates  with  a  recip- 
rocal motion  produced  by  the  flow  of  an  alternating 
electric  current  through  one  or  the  other  of  two 
solenoids,  of  which  the  drill  stock  is  the  core. 

Electro-Photometer. — An  instrument  which  measures 
the  intensity  of  light  by  the  application  of  elec- 
tricity. 

Electro-Plating. — A  process  for  coating  conducting  sur- 
faces with  a  metallic  deposit  by  means  of  an  elec- 
tric current. 

Electro-Plating  Bath. — A  tank  holding  a  metallic  solu- 
tion into  which  articles  to  be  electro-plated  are 
immersed. 

Electro-Pyrometer. — An  apparatus  used  to  ascertain 
the  degrees  of  temperature  by  measuring  the  re- 


ELECTRICAL  DICTIONARY  Bl 

•sistance  of  a  platinum  wire  which  has  been  sub- 
jected to  the  action  of  the  temperature  to  be 
determined. 

Electro-Siliceous  Light. — A  brilliant  incandescence  ob- 
tained in  a  glass  tube  by  the  discharge  through  it 
of  a  powerful  static  machine;  the  tube  being 
crossed  by  a  platinum  wire  and  immersed  in  salt 
water,  resulting  in  the  melting  and  volatilization  of 
the  wire  by  the  intense  heat  of  the  discharge. 

Electro- Smelting. — The  separation  of  metals  from  the 
ores  by  means  of  electrically  generated  heat,  i.  e. : 
heat  generated  by  electric  currents. 

Electro-Therapeutics. — The  use  of  electricity  in  the 
treatment  of  the  human  body  for  disease. 

Electro-Thermic. — Pertaining  to  the  application  of 
electricity  for  generating  heat. 

Electro-Tinning. — The  electro-plating  or  coating  of  a 
substance  with  tin. 

Electro-Type. — The  electrolytic  deposition  of  metals  in 
a  mould  in  order  to  obtain  a  fac-simile. 

Electro-Type. — The  impression  of  type  produced  by  the 
electro-metallurgic  process. 

Electro-Type  Process. — The  process  by  which  an  im- 
pression or  cast  of  type  is  produced  by  means  of 
electro-metallurgy. 

Electrocution. — Execution  of  the  death  penalty  by 
means  of  an  electric  shock. 

Electrode. — The  one  or  the  other  of  electric  source  ter- 
minals which  is  put  into  a  solution  where  electro- 
lysis is  going  on.  One  or  the  other  of  the  electro- 
therapeutic  terminals  of  an  electric  source. 


82  ELECTRICAL  DICTIONARY 

Electrolier. — A  fixture  serving  to  hold  electric  lamps  as 
distinguished  from  one  designed  for  gas  burners. 

Electrolier  Cut-Out. — A  cut-out  employed  in  the  circuit 
of  an  electrolier. 

Electrolier  Switch. — A  switch  serving  to  light  and  ex- 
tinguish lamps  in  an  electrolier. 

Electrolysis. — The  process  of  chemical  decomposition 
by  the  action  of  an  electric  current.  The  dissolu- 
tion of  the  molecule  of  an  electrically  decomposa- 
ble compound  into  its  radicals. 

Electrolyte. — A  compound  decomposable  or  subjected 
to  decomposition  by  an  electric  current. 

Electrolytic  Assaying. — Assaying  by  aid  of  electrolysis. 

Electrolytic  Corrosion. — The  corrosion  of  metallic  pipes 
or  other  metallic  material  buried  in  the  ground 
resulting  from  electrolytic  action. 

Electrolytic  Decomposition. — The  dividing  of  a  mole- 
cule into  its  component  ions  or  radicals  by  means 
of  an  electric  current. 

Electrolyze. — To  electrically  separate  or  decompose. 

Electrometer  Fatigue. — The  elastic  exhaustion  of  an 
electrometer's  needle  suspension  resulting  in  its 
failure  to  return  to  the  zero  point. 

Electromotive  Force. — The  cause  which  produces  cur- 
rents of  electricity.  Potential  difference  causing 
a  current  to  flow. 

Electromotograph. — An  apparatus  having  a  rotating 
cylinder  of  chalk  moistened  with  a  solution  of 
caustic  soda  and  a  diaphragm  with  an  arm  pointed 
with  platinum,  connected  to  its  center  and  pressed 
against  the  surface  of  the  cylinder  by  a  spring, 


ELECTRICAL  DICTIONARY  83 

the  point  being  reduced  by  electrolytic  action  in- 
cident to  the  flow  of  the  electric  current. 

Electromotographic  Telephone. — A  telephone  for  loud 
speaking  and  operated  on  the  electromotographic 
principle. 

Electron. — A  word  signifying  amber,  not  obsolete,  but 
seldom  used.  An  alloy  of  gold  and  silver.  The 
throwing  of  electric  particles  from  the  cathode  of 
a  high  vacuum  tube. 

Electropoion  Liquid. — A  depolarizing  solution  consist- 
ing of  one  part  of  bichromate  of  potash  dissolved 
in  ten  parts  of  water,  with  two  parts  of  sulphuric 
acid  added  gradually. 

Electroscope. — An  apparatus  for  indicating  the  pres- 
ence of  an  electric  charge,  and  for  determining  its 
character,  as  to  the  positive  or  negative  state  of 
the  charge,  without  measuring  its  amount  of  value. 

Electrostatic  Discharge. — A  term  used  to  express  a  dis- 
ruptive discharge. 

Electrostatic  Generator. — A  term  used  in  general  ap- 
plication to  divers  forms  of  influence  machines. 

Electrostatic  Induction-Machine. — A  machine  from  the 
initial  charge  of  which  proceeds  a  charge  greatly 
increased  by  its  inductive  action  on  a  plate  of  glass 
or  other  dielectric,  rapidly  rotated. 

Electrum. — An  alloy  of  gold  and  silver  and  other  sub- 
stances of  an  amber  color  used  by  the  ancients  and 
which  were  susceptible  to  electrification  by  friction. 

Element. — One  of  the  ultimate,  indecomposable  con- 
stituents of  any  kind  of  matter. 

Element  of  Storage  Battery. — One  set  only  of  positive 
and  negative  plates  of  a  storage  cell  connected  in 


84  ELECTRICAL  DICTIONARY 

such  manner  as  to  be  prepared  to  be  put  into  the 
containing  jar  of  acid  liquid. 

Elevator  Annunciator. — An  annunciator  in  an  elevator 
connected  with  the  different  floors  from  which  sig- 
nals are  received. 

Elevator,  Electric. — An  elevator  whose  motive  power 
is  derived  from  electricity. 

Elevator  Switch. — A  switch  located  in  an  elevator  and 
serving  to  control  the  working  of  the  elevator 
motor. 

Elliptical  Rotary-Magnetization. — The  magnetization 
manifested  in  a  diphase  motor  where  two  alternat- 
ing magnetic  currents  exist  at  the  same  time,  each 
one  out  of  phase  with  the  other. 

Emergency  Brake. — A  brake  adjusted  to  any  vehicle  to 
be  used  in  an  emergency  only.  A  brake  used  in 
electrical  vehicles  in  cases  of  emergency  only ;  pos- 
sessing more  than  ordinary  power  and  serving  as 
a  reversing  switch  to  immediately  reverse  the  ro- 
tating direction  of  the  motor. 

Emergency  Crew. — A  gang  of  men  attached  to  a  power 
distribution  system  and  assigned  to  emergency 
duty,  consisting-  of  prompt  attention  and  restora- 
tion in  cases  of  break  down  or  other  irregularities. 

Emergency  Switch. — An  auxiliary  switch  used  on  a  car 
controller  to  reverse  the  motion  of  a  car  when  re- 
quired. 

Emmetropic  Eye. — The  human  eye  in  its  normal  condi- 
tion. 

Enamelled  Rheostat. — A  rheostat  the  wire  coils  of 
which  are  deposited  in  a  quantity  of  enamel. 


ELECTRICAL  DICTIONARY  85 

Enclosed  Arc-Lamp. — A  lamp  with  a  closely  fitting 
globe  which  encloses  the  carbon  so  as  to  secure 
around  the  arc  an  atmosphere  with  practically  no 
oxygen,  by  reason  of  which  the  rate  of  consump- 
tion of  the  carbon  is  decreased. 

Enclosure  of  Magnetic  Flux. — Enclosing  magnetic  flux 
in  a  ferric  magnetic  circuit.  The  linkage  of  the 
flux. 

Endlessness. — The  state  of  a  closed  ring  and  of  uniform 
cross  section,  magnetizing  coils  being  uniformly 
wound  around  it,  thereby  securing  throughout  the 
length  of  the  ring  a  practically  uniform  magnetic 
field. 

Endosmose. — The  unequal  blending  of  two  different 
fluids  in  the  penetration  of  any  intervening  porous 
structure. 

Endosmose,  Electric. — The  uneqaal  blending  of  two 
liquids  through  the  pores  of  a  partition,  separating 
cells;  where  an  electric  current  is  made  to  pass 
through  the  partition  or  septum. 

Energy. — Power  efficiently  and  forcibly  exerted. 

Energy  Efficiency  of  Storage  Battery.— The  Watt-hour 
efficiency. 

Energy,  Electric. — Power  efficiently  exerted  by  elec- 
tricity in  the  performance  of  work. 

Energy  Meter. — A  name  given  to  a  Watt-meter. 

Energy  of  Motion. — A  term  applied  to  kinetic  energy. 

Engine-Room  Tachometer. — A  tachometer  designed  for 
use  in  connection  with  engines,  dynamos  and  ro- 
tating machinery  generally  in  engine  rooms. 

English  Heat  Unit.— The  British  unit  of  heat.  The  heat 
required  to  raise  one  pound  of  water  1  degree  F. 


86  ELECTRICAL  DICTIONARY 

Entrefer. — The  opening  of  non-magnetic  substance 
through  which  the  field  flux  must  pass  in  a  dyna- 
mo-electric machine's  surface,  formed  of  air  or 
composed  of  an  air  gap.  The  breadth  of  the  non- 
magnetic gap  in  distinction  from  a  smooth-cored 
armature's  simple  air  gap. 

Equalizer. — A  term  applied  to  an  equalizer  wire.  A 
device  by  use  of  which  electric  pressure  over  a 
system  is  equalized.  An  equalizing  bar. 

Equalizer  Wire. — An  equalizing  bar.  A  wire  by  which 
the  series  windings  of  several  compound-wound 
generators  are  operated  in  parallel. 

Equalizing  Bar. — A  bar  uniting  the  series  coils  of  two 
compound-wound  generators  connected  in  parallel, 
thus  providing  that  a  surplus  of  current  furnished 
by  the  armature  of  one  machine  will  of  necessity 
excite  the  other  machine  to  a  like  degree. 

Equator  of  Magnet. — A  point  nearly  half  way  between 
the  poles  of  a  straight  bar  magnet  or  approximately 
half  way  from  the  poles  of  a  horseshoe  magnet  if 
measured  from  each  pole  along  the  bar.  The 
neutral  point  line  on  a  magnet. 

Equilibrium. — A  state  of  rest  produced  by  the  mutual 
counter-action  of  two  or  more  forces. 

Equipotential. — Pertaining  to  an  equality  of  potential. 

Equipotential  Magnetic-Surfaces. — Surfaces  which  sur- 
round the  poles  of  a  system  of  magnets  or  one 
magnet  at  which  the  magnetic  potential  is  the  same. 

Equivalent  Air-Gap. — An  air  gap  which  would  possess 
magnetic  resistance  equal  to  that  of  a  joint,  sup- 
posing the  penetrability  of  the  metal  not  to  be  af- 
fected by  cutting. 


ELECTRICAL  DICTIONARY  87 

Erg, — The  absolute  C.  G.  S.  unit  of  work  or  energy. 

The  work  done  or  energy  expended  in  moving  a 

body  through  one  centimeter  or  against  a  resistance 

of  one  dyne  in  one  second. 
Erg-Meter. — An  instrument  for  measuring  in  ergs  the 

performance  of  an  electric  current. 
Ether. — A  hypothesis  of  a  highly    attenuated  electric 

fluid  in  universal  space,  the  transverse  vibrations 

of  which  transmit  light,  electro-magnetic  and  heat 

radiation. 
Ether  Flow  Vortices. — Hypothetical  vortices  in  ether, 

whose  supposed  existence  furnishes  a  basis  upon 

which  magnetic  phenomena  are  explained. 
Evaporation. — The  act  or  process    of    solids  or  fluids 

turning  into  or  passing  off  in  vapor. 

Evaporation,  Electric. — The  superficial  sublimation  or 
evaporation  of  a  substance  under  the  influence  of 
negative  electricity. 

Excitation. — The  generation  of  electricity  or  production 
of  magnetism  by  any  method.  The  energizing  of 
an  electro  or  magneto-receptive  contrivance. 

Exciter  Dynamo. — One  dynamo  employed  for  the  ex- 
citation of  another. 

Exciter  of  Field. — A  generator  used  for  exciting  the 
field  magnet  of  a  dynamo. 

Exhaust  Fan,  Electric. — An  exhaust  fan  operated  by 
electricity. 

Exhaust  Wheel,  Electric. — An  exhaust  wheel  operated 
by  electricity  and  serving  to  exhaust  the  air  from 
an  apartment. 

Exhausted  Storage  Cell. — A  storage  cell  which  has  been 
emptied. 


88  ELECTRICAL  DICTIONARY 

Expansion. — The  act  of  expanding  or  spreading  out. 
The  act  of  increasing  in  volume,  length  or  surface. 

Expansion,  Electric. — The  increase  in  volume  of  a  con- 
denser when  charged  electrostatically. 

Expansion  Joint. — A  joint  adaptable  to  pipes  or  tubes 
which  are  exposed  to  changes  of  temperature  and 
which  is  equipped  with  a  sliding  joint  to  provide 
for  expansion  and  contraction. 

Expended  Energy. — The  energy  consumed  in  obtaining 
a  result. 

Extension  Call-Bell. — A  bell  connected  with  a  telephone 
call  bell  and  located  in  another  part  of  a  building 
and  serving  to  summon  a  subscriber  to  the  tele- 
phone from  a  remote  part  of  the  building. 

Extension  Push  Button. — A  push  button  located  at  a 
distance  from  the  main  push  button. 

External  Armature  Generator. — A  generator  whose 
armature  is  outside  of  the  field  frame. 

External  Magnetic  Circuit. — The  section  of  a  magnetic 
circuit  lying  outside  the  magnetic  source.  That 
part  of  a  magnetic  circuit  lying  outside  of  its 
core. 

External  Magnetic  Field. — That  part  of  a  magnetic  field 
lying  outside  of  a  magnet's  body. 

Extra-High-Potential  System.— A  potential  over  3,000 

volts,  in  the  National  Electric  Code. 
Extraneous  Field. — A  leakage  of  magnetic  field. 


ELECTRICAL  DICTIONARY 


Factor. — One  of  the  elements  or  quantities  which  multi- 
plied together  form  a'product. 

Factor  of  Safety. — The  relation  of  the  reckoned  or 
measured  strength  of  a  structure  to  the  maximum 
strength  it  will  be  required  to  exert. 

Fahrenheit  Thermometric  Scale. — The  division  of  the 
thermometer  scale  into  180  equal  degrees,  along 
the  length  of  the  tube,  between  the  melting  point 
of  ice  and  the  boiling  point  of  water. 

Fall-Back  Indicator. — A  name  given  to  a  drop  indicator. 

Fall  of  Potential. — Potential  drop. 

False  Zero. — A  zero  of  an  instrument  used  for  measur- 
ing, the  zero  being  taken  at  the  position  it  assumes 
naturally  under  the  influence  of  other  forces  than 
those  impressed  in  the  measurement. 

Fan  Motor. — An  electric  motor  used  for  operating  a 
fan. 

Farad. — The  practical  unit  of  electric  capacity.  That 
capacity  possessed  by  a  conductor  which  is  capable 
of  holding  one  coulomb  of  electricity  at  one  volt 
potential. 

Faraday's  Cube. — A  room  insulated  and  lined  with  tin- 
foil which  makes  no  electrical  indications  on  the 
most  delicate  instruments  on  the  inside  of  the  room 
when  the  room  has  been  charged  on  the  outside. 

Faradic  Adapter. — A  contrivance  by  means  of  which 
ordinary  incandescent  light  circuits  can  be  used 
in  electro-therapeutics,  with  an  induction  coil. 

Faradic  Coil. — A  name  given  to  a  medical  induction  coil 
or  faradic  machine. 


90  ELECTRICAL  DICTIONARY 

Faradic  Current. — A  term  employed  in  medical  elec- 
tricity for  the  induced  or  secondary  alternating 
current  produced  by  comparatively  high  electro- 
motive force. 

Faradic  Machine. — A  machine  serving  to  produce  fara- 
dic  currents. 

Fathom. — A  measure  of  length  containing  six  feet. 

Fault. — A  defect  in  the  efficient  operation  of  a  circuit 
caused  by  ground  and  cross  contacts  or  disconnec- 
tions. 

Fault  Resistance. — That  resistance  which  is  due  to  a 
fault. 

Feed. — To  furnish  an  electric  current.  To  regulate  the 
carbon  electrodes  in  arc  lamps. 

Feeder. — A  conducting  wire  through  which  the  current 
flows  for  distribution  to  the  main  conductors,  thus 
differing  from  a  conductor  which  serves  to  supply 
translating  devices  directly. 

Feeder  Ammeter. — An  ammeter  located  in  the  circuit 
of  a  feeder  generally  at  a  switchboard. 

Feeder  Block. — A  block  having  a  feeder  cut-out. 

Feeder  Box. — A  box  used  for  distribution  and  into 
which  a  feeder  has  been  run  to  receive  the  dis- 
tributing connections. 

Feeder-Mechanism  for  Arc-Lamp. — The  mechanism 
used  to  feed  an  arc  lamp. 

Feeders. — Wires  which  furnish  the  main  conductors 
with  currents  at  different  points  whereby  their 
potential  under  load  is  equalized,  hence  differing 
from  wires  which  furnish  the  currents  directly. 

Feeding  Device  or  Mechanism  for  Electric  Arc-Lamps. 
— A  contrivance  which  keeps  the  carbon  electrodes 


ELECTRICAL  DICTIONARY  91 

of  an  arc  lamp  'separated  by  a  regular  distance 
during  the  time  they  are  being  consumed. 

Fender. — A  form  of  pilot  employed  on  the  front  of 
street  cars  to  guard  against  accidental  injury  to 
persons  crossing  in  front  of  a  moving  car. 

Ferric  Inductance  Coil. — An  inductance  coil  having  an 
iron  core. 

Ferric  Magnetic  Circuit. — A  magnetic  circuit  consist- 
ing of  iron  entirely. 

Ferro-Magnetism. — Magnetism  which  iron  and  other 
paramagnetic  substances  possess. 

Ferro-Manganese  Alloys. — Divers  alloys  used  for  the 
wires  of  resistance  coils,  the  electric  resistance  of 
which  is  not  noticably  influenced  by  changes  of 
temperature. 

Field. — A  term  signifying  a  magnetic  and  an  electro- 
static field. 

Field  Coils. — The  field-magnet  coils  of  a  motor  or 
dynamo-electric  machine. 

Field  Frequency. — The  frequency  of  rotation  in  a  re- 
volving magnetic  field. 

Field  Magnetic  Coils. — Magnetizing  coils  on  the  field 
magnets  of  a  motor  or  dynamo. 

Field  Magnets. — Magnets,  generally  electro-magnets,, 
used  to  produce  the  field  in  a  dynamo  or  motor. 

Field-Regulating  Box. — A  resistance  box. 

Field  Rheostat. — A  field  regulating  box. 

Field  Strength. — The  intensity  of  the  magnetic  force  of 
a  field. 

Filament. — A  fine  thread  or  fiber. 

Filament  of  Incandescent  Lamp. — The  conductor  of  an 
incandescent  lamp  which  becomes  incandescent. 


92  ELECTRICAL  DICTIONARY 

Film. — A  term  used  to  describe  a  thin  layer  or  deposit 

obtained  by  electro-plating. 
Filtration. — The  elimination  of  undissolved  solids  from 

the   liquid   in  which  they   are   mechanically   sus- 
pended. 
Fire-Alarm  Annunciator. — An  annunciator  employed  in 

fire  alarm  systems. 
Fire-Alarm  Signal  Box. — A  signal  box  located  in  the 

street  or  other  convenient  place  from  which  alarms 

of  fire  are  sent. 
Fire-Alarm  Telegraph. — A  term  applied  to  the  whole 

apparatus  used  in  fire-alarm  telegraphy. 
Fish  Plate. — The  plates  used  with  bolts  to  connect  the 

track  rails  on  railroads. 
Fished  Wires. — Wires  which  have  been  put  into  ducts 

by  means  of  the  fishing  process. 
Flashing  Box. — A  term  at  times  applied  to  a  junction 

box. 

Fishing  Wires. — The  process  by  which  a  wire  is  drawn 
into  its  place  through  the  walls,  ceiling  or  floors  of 
a  building  and  which  is  accomplished  by  inserting 
the  wire  into  a  hole  at  one  point  and  hooking  it 
from  another  and  then  drawing  it  through. 

Fiske's  Electric  Range  Finder. — A  device  employed  to 
obtain  the  distance  of  an  object  from  the  point  of 
observation,  and  signally  useful  in  locating  the 
exact  distances  of  targets  or  an  enemy's  ship  at  sea. 

Five-Wire  System. — A  system  resembling  the  three- 
wire  system  in  its  construction,  wherein  four 
series  connected  dynamos  are  connected  to  five  con- 
ductors. 

Fixed  Resistance. — A  resistance  having  a  nearly  con~ 


ELECTRICAL   DICTIONARY  93 

stant  value,  thus  differing  from  a  regulable  resist- 
ance. 

Fixture  Electric. — Fixtures  for  electric  lights.  A  fix- 
ture for  the  accommodation  of  one  or  more  incan- 
descent lamps  firmly  attached  to  wall  or  ceiling. 

Fixture  Wire. — A  style  of  insulated  wire  used  in 
electric  fixtures. 

Flag  Signaling. — A  system  of  semaphore  signaling  con- 
sisting of  the  waving  of  a  light  flag  upon  the 
Morse  alphabetical  system,  the  dots  being  repre- 
sented by  movements  of  the  flag  to  the  right  and 
the  dashes  by  movements  to  the  left. 

Flaming  of  Carbon  Arc. — An  irregularity  in  the  burn- 
ing of  a  voltaic  arc  which  manifests  itself  when  the 
carbons  are  too  far  from  each  other  and  the 
strength  of  current  is  greater  than  the  normal. 

Flashed  Carbon  Filaments. — Carbon  filaments  which 
have  been  improved  by  means  of  the  flashing  pro- 
cess. 

Flashing  of  Dynamo-Electric  Machine. — A  name  for  the 
phenomena  of  long  flashes  and  sparks  at  the  com- 
mutator of  a  dynamo  resulting  from  the  short 
circuiting  of  the  external  circuit  at  commutator. 

Flashing  Process  for  Carbon  Filaments. — A  process  of 
treatment  for  the  filaments  of  incandescent  lamps 
whereby  improvement  is  made  by  the  deposit  of 
carbon  in  the  pores  and  over  the  surfaces  of  the 
filaments,  which  is  accomplished  by  subjecting  the 
filaments  to  an  incandescence,  while  surrounded  by 
a  carbonaceous  fluid. 

Flat  Commutator-Segment. — A  commutator  segment 
whose  surface  has  become  flat  from  burning  or 
wearing  away. 


94  ELECTRICAL  DICTIONARY 

Flat-Iron,  Electric. — A  flat-iron  heated  by  electricity. 

Flexible. — Capable  of  easily  bending. 

Flexible  Cable. — A  cable  which  can  be  easily  bent  or 
flexed. 

Flexible  Conduit  System. — A  system  of  conduits  so 
devised  that  the  conductors  which  the  conduits  are 
to  contain  can  be  introduced  at  any  time  after  com- 
pletion. 

Flexible  Electric-Light  Pendant. — -An  incandescent 
lamp  pendant  composed  of  a  pair  of  conductors 
insulated  from  each  other  and  flexible. 

Flexible  Lamp-Cord. — A  flexible  cord  serving  to  hold 
an.  incandescent  lamp.  A  flexible  cord  having  a 
connection  with  an  incandescent  lamp,  to  some 
extent  portable. 

Flow. — The  volume  of  a  current  or  stream  of  any  fluid 
escaping  from  an  opening  in  a  given  time.  The 
volume  of  fluid  passing  by  a  certain  point  in  a 
given  time. 

Flow  of  Energy. — The  passage  ,of  energy  through  the 
medium  by  which  a  conductor  is  surrounded  and 
now  accepted  as  the  cause  of  the  electrical  current, 
which  was  formerly  supposed  to  flow  through  the 
conductor. 

Flow  of  Magnetic  Flux. — The  amount  of  magnetic  flux 
which  flows  through  a  magnetic  circuit  under  a 
certain  magneto-motive  force  in  opposition  to  a 
certain  magnetic  reluctance. 

Fluctuating  Electromotive  Force  or  Current. — An 
electromotive  force  which  periodically  undergoes 
variations  of  magnitude. 

Fluidity. — Having  fluid  properties. 


ELECTRICAL  DICTIONARY  95 

Fluorescence. — That  property  by  virtue  of  which  cer- 
tain solids  and  fluids  become  luminous  under  the 
influence  of  radiant  energy. 

Fluorescent  Screen. — A  screen  bearing  fluorescent 
materials  on  its  surface. 

Fluoroscopic  Examination. — An  examination  of  a  body 
by  means  of  an  X-ray  and  a  fluorescent  screen. 

Fluoroscopic  Screen. — A  screen  overspread  with  fluo- 
rescent material  and  employed  for  fluoroscopic  ex- 
amination in  connection  with  X-rays. 

Flush  Box. — An  iron  box,  covered  with  a  heavy  hand 
plate  and  laid  flush  or  even  with  the  surface  and 
employed  in  systems  of  conduits,  to  make  con- 
nections therewith  and  to  examine  the  leakage  of 
conductors,  or  for  like  purposes. 

Flush  Key-Switch. — A  key  switch  which  is  flush  or 
even  with  the  wall  in  which  it  is  located. 

Flush  Switch. — A  switch  imbedded  in  the  wall  in  such 
manner  as  to  leave  its  outer  surface  even  or  flush 
with  the  surface  of  the  wall. 

Flux. — Magnetic  induction;  the  number  of  lines  of 
force  which  pass  through  a  magnetic  circuit. 

Flux  Density. — The  intensity  of  magnetization  ex- 
pressed in  lines  of  force  per  unit  of  area  of  cross- 
section  in  a  plane  at  right  angles  to  the  lines  of 
force. 

Focal  Length. — The  distance  between  a  focus  and  lens. 
The  distance  from  the  optical  center  of  a  lens 
where  parallel  rays  come  to  a  focus. 

Focus. — A  point  in  which  the  rays  of  light  meet  after 
being  reflected  or  refracted ;  as  the  focus  of  a  lens 
or  mirror. 


96  ELECTRICAL  DICTIONARY 

Focusing. — Modifying  the  distance  between  an  object 
and  a  lens  or  mirror  for  the  purpose  of  producing 
a  clean-cut  image  of  the  object. 

Focusing  Arc-Lamp. — An  arc  lamp  used  with  a  reflec- 
tor or  lens  and  so  constructed  that  its  mechanism 
feeds  both  carbons  in  such  a  manner  as  to  keep 
the  arc  at  the  focus  of  the  reflector. 

Foot-Pound. — A  unit  of  work.  The  work  necessary 
to  raise  a  pound  vertically  the  distance  of  a  foot. 

Foot-Pound-Per-Second. — A  rate  of  performance  equal 
to  one  foot  pound  expended  per  second. 

Force. — Any  action  between  two  bodies  which  changes 
or  tends  to  change  their  relative  conditions  as  to 
rest  or  motion. 

Force  Pump. — A  pump  having  a  solid  piston  and  serv- 
ing to  raise  liquids  vertically  to  a  greater  height 
than  they  could  be  raised  by  atmospheric  pressure. 

Fork  for  Trolley  Wheel. — A  device  by  means  of  which 
the  trolley  wheel  and  pole  are  connected. 

Formed  Armature- Windings. — Coils  of  an  armature 
that  are  wound  first  on  a  form  and  then  placed  on 
the  armature  core. 

Formers. — The  forms  used  in  producing  formed  arma- 
tures and  like  windings. 

Forming  Storage-Battery  Plates. — Causing  heavy  de- 
posits of  peroxide  of  lead  and  spongy  lead  re- 
spectively on  the  lead  plates  of  a  storage  battery, 
by  passing  a  charging  current  between  them  alter- 
nately in  opposite  directions  while  they  are  im- 
mersed in  dilute  sulphuric  acid. 

Formulae. — A  rule  or  principle  expressed  in  algebraic 
language. 


ELECTRICAL  DICTIONARY  97 

Forward  Lead  of  Dynamo  Brushes. — The  displacement 
of  the  brushes  on  a  dynamo's  commutator  in  the 
direction  in  which  the  armature  rotates. 

Foucault  Currents. — A  term  expressive  of  eddy  cui* 
rents,  particularly  when  in  armature  cores.  Use- 
less currents  created  in  a  conducting  mass  by  the 
movement  through  magnetic  flux. 

Fountain,  Electric. — A  fountain  worked  by  electric 
motors  and  equipped  with  a  number  of  jets  which 
when  electrically  illuminated  display  lights  of  dif» 
ferent  colors. 

Fountain  Projector. — An  arc  light  projector  by  means 
of  which  the  jets  of  an  electric  fountain  are 
illuminated. 

Four-Point  Switch. — A  switch  capable  of  having  its 
circuit  completed  through  four  points,  either  one 
at  a  time  or  simultaneously.  A  four-pole  switch. 

Four-Pole  Dynamo-Electric  Machine. — A  dynamo-elec- 
tric machine  the  magnet  field  of  which  is  produced 
by  four  magnet  poles. 

Four-Speed  Regulator. — A  regulator  having  a  motor 
capable  of  giving  four  different  speeds. 

Four-Wire  System. — A  system  resembling  in  its  gen- 
eral order  of  form  the  three-wire  system,  which 
provides  for  the  connection  of  three  dynamos  to 
four  wires  or  conductors. 

Fractional  Distillation. — The  evaporation  of  liquids 
by  heat,  providing  for  the  separation  of  two  or 
more  liquids  by  first  obtaining  the  degree  of  heat 
at  which  the  most  volatile  liquid  will  boil,  and 
when  it  has  been  evaporated  the  degree  of  temper- 
•ature  is  raised  sufficiently  to  evaporate  the  next 


98  ELECTRICAL  DICTIONARY 

most  volatile  liquid,  and  so  on  in  order  until  all 
are  evaporated.  The  separation  of  liquids  by  dis- 
tillation in  their  successive  order  of  increased  tem- 
perature required  for  volatilization. 

Fractional  Electrolysis. — The  electrolysis  of  various 
substances  by  successively  raising  the  E.  M.  F. 

Franklinic  Currents. — Currents  created  by  a  frictional 
induction  machine. 

Free  Ether. — A  name  given  to  the  ether  which  fills 
inter-planetary  space  in  distinction  from  the  inter- 
atomic or  inter-molecular  ether. 

Free  Vibrations. — Vibrations  in  a  body  susceptible  of 
elastic  vibration  produced  by  the  vibration  of  a 
neighboring  vibrating  body. 

Freezing. — To  become  congealed  by  cold;  to  become 
changed  from  a  liquid  to  a  solid  state  by  the  ab- 
straction of  heat. 

Freezing  Mixtures. — Mixtures  composed  of  such  mater- 
ials as  salt  and  ice,  which  melt  rapidly  when 
mixed,  thereby  absorbing  the  heat  from  surround- 
ing or  contiguous  substances. ' 

Freezing  Point. — The  point  at  which  liquids  congeal. 

Frequencjr  of  Alternation. — The  periodicity.  The  num- 
ber of  cycles  accomplished  in  a  unit  of  time  by  an 
alternating  current. 

Friable. — Readily  reduced  to  powder,  pulverized  or 
crumbled. 

Friction. — The  effect  of  rubbing.  The  resistance  which 
a  moving  body  meets  with  by  the  contact  of  an- 
other body. 

Friction  Brake. — A  form  of  brake  which  accomplishes 
the  result  by  friction. 


ELECTRICAL  DICTIONARY  99 

Frictional  Torque. — The  torque  in  a  motor  which  is 
required  to  be  exerted  on  the  armature  in  order 
to  neutralize  the  friction.  Torque  produced  by 
friction. 

Frog. — A  triangular  crossing  support  and  guide  for  the 
wheels  of  a  car  where  one  track  branches  off  from 
another  or  crosses  it  at  an  angle  greater  or  less 
than  a  right  angle,  and  which  permits  a  car  or 
train  to  leave  one  track  and  enter  upon  another. 

Frying  of  Arc. — A  hissing  noise  resembling  the  sound 
of  frying  noticeable  in  voltaic  arcs  when  carbons 
are  too  close  together. 

Full  Load. — A  complete  load.  The  greatest  load  which 
a  machine  is  intended  to  permanently  carry. 

Full-Load  Efficiency  of  Motor. — A  motor's  efficiency 
when  working  under  full  load. 

Full-Loud  Efficiency  of  Transformer. — A  transformer's 
efficiency  or  the  relation  of  the  power  rendered  at 
secondary  terminals  to  that  which  is  taken  in  at 
primary  terminals,  when  working  under  full  load. 

Fulminate. — A  term  applied  to  explosives  of  high  ex- 
plosive properties. 

Fundamental  Units. — Units  of  dimension,  mass  and 
time  to  which  all  quantities  >are  referred,  and 
which  are  distinct  from  derived  units. 

Furnace,  Electric. — A  furnace  in  which  the  heat,  elec- 
trically generated,  is  used  to  produce  difficult 
fusions  whereby  metals  are  separated  from  the 
ores,  and  also  for  the  prosecution  of  other  metal- 
lurgical operations. 

Fuse  Block. — A  block  having  a  safety  fuse. 

Fuse    Board. — A    board    made    of    an    incombustible 


100  ELECTRICAL  DICTIONARY 

material,  usually  slate,  upon  which  a  number  of 

safety  fuses  are  mounted. 
Fuse  Box. — An  incombustible  box  containing  a  safety 

fuse  or  fuse  wires. 
Fuse  Links. — Links   composed  of  strips  or  plates  of 

fusible  metal,  serving  as  safety  fuses. 
Fuse  Panel. — A  panel  in  a  switchboard  designed  to  sup- 
port the  safety  fuses. 
Fusible  Plug. — A  name  sometimes  used  for  a  safety 

plug. 
Fusing  Current. — A  term  signifying  the  quantity  of 

current  which  causes  the  blowing  or  melting  of  a 

fuse. 


Galvanic  Adapter. — An  apparatus  by  means  of  which 
feeble  continuous  currents  are  obtained  from  an 
electric  light  circuit  for  use  usually  in  electro- 
therapeutic  treatment. 

Galvanic  Battery. — A  term,  now  misapplied,  but  some- 
times used  to  signify  a  voltaic  battery. 

Galvanic  Electricity. — A  term,  now  misapplied,  but 
sometimes  used  to  signify  voltaic  electricity. 

Galvanic  Multiplier. — A  term  practically  obsolete,  once 
applied  to  a  galvano-meter. 

Galvanic  Taste. — A  taste  resulting  from  the  passage 
through  the  tongue  of  a  voltaic  current. 

Galvanized. — Subjected  to  galvanic  action.  The  coat- 
ing of  a  metal  with  zinc  by  cleaning  and  immers- 
ing in  melted  zinc. 


ELECTRICAL   DICTIONARY    ,     ,  ,     ,  101 

Galvanized  Iron. — Iron  covered'  with  a  coating  of  zinc. 

Galvanized  Iron  Wire. — An  iron  wire  zinc  coated. 

Galvanizing. — Coating  iron  with  a  layer  of  zinc  by  im- 
mersion in  the  melted  metal.  '  Subjecting  the 
nerves  or  muscles  of  the  human  body  to  galvanic 
influences. 

Galvanometer. — An  instrument  for  measuring  electric 
current  strength  by  the  deflection  of  an  electric 
needle. 

Galvano-Plastic  Matrix. — A  mould  serving  for  the 
reception  of  a  galvano-plastic  deposit. 

Galvano-Plastics. — A  term  applied  to  electrotyping,  or 
the  process  by  which  is  obtained  electrolytic 
deposits  of  such  sufficient  body  upon  any  suitable 
object  as  to  permit  of  its  convenient  separation 
therefrom. 

Galvanoscope. — A  crude  instrument  of  the  galvanome- 
ter type,  employed  for  ascertaining  whether  or  not 
a  current  is  flowing. 

Gap  Wire  Gauge. — A  style  of  gauge  for  measuring 
wires,  having  a  metallic  plate  that  contains  gaps 
or  sets  of  gaps  which  may  be  bridged  or  filled  by 
the  wire  to  be  measured. 

Gas  Engine. — An  engine  deriving  its  motive  power 
from  heat  generated  by  burning  or  exploding  gas. 

Gas-Jet  Photometer. — A  photometer  in  which  a  burning 
gas  jet  represents  the  standard  of  light  and  which 
burns  with  or  without  a  diaphragm  at  a  definite 
height  and  under  standard  conditions  of  pressure 
and  volume. 

Gas-Lighting,  Electric. — The. ignition  of  a  gas  jet  from 
a  distance  by  electricity. 


102  ELECTRICAL  DICTIONARY 

Gassing. — The  development  of  gas  from  secondary  or 
storage  battery  plates. 

Gauze  Brushes  for  Dynamo  or  Motor. — Collecting  or 
commutator  brushes  for  a  dynamo  composed  of 
wire  gauze  compressed  into  suitable  shape. 

Gearless  Car  Motor. — A  motor  the  speed  capacity  of 
which  allows  it  to  be  directly  connected  on  the  car 
wheel  axle  without  interjacent  gearing. 

Geissler  Mercurial  Pump. — A  mercurial  air  pump  which 
exhausts  by  the  Torricellian  vacuum  principle. 

Geissler  Tubes. — Sealed  tubes  of  glass  containing 
highly  rarefied  gases,  either  with  or  without  fluo- 
rescent liquids  or  solids  or  both,  and  provided  with 
platinum  electrodes  passing  through  and  fused  into 
the  glass,  luminous  effects  being  produced  on  the 
passage  of  the  electric  discharges. 

Generator. — A  dynamo-electric  machine. 

Generator  Ammeter. — An  ammeter  designed  to  measure 
the  total  current  sent  out  by  a  generator. 

Generator  Bus-Bars. — The  copper 'conductors  used  in 
electric  lighting  or  power  stations  to  receive  the 
current  from  all  the  dynamos. 

Generator  Panels  of  Switchboard. — The  panels  of  a 
central  station  switchboard  upon  which  the  gen- 
erator bus-bars  are  mounted  and  which  maintain 
the  switches,  generator  ammeters  and  volt-meters. 

Generator  Switch. — A  switch  serving  to  connect  or  dis- 
connect a  generator  from  the  bus-bars. 

Generator  Voltmeter. — A  voltmeter  serving  to  measure 
the  pressure  of  the  generator  with  whose  circuit 
it  is  connected. 


ELECTRICAL  DICTIONARY  103 

Geographical  Equator. — The  great  imaginary  line  en- 
circling the  earth  midway  between  the  poles. 

Geographical  Meridian. — Any  great  imaginary  line  en- 
circling the  earth  in  the  direction  of  and  passing 
through  the  poles  and  cutting  the  equator  at  right 
angles. 

German-Silver  Alloy. — An  alloy  composed  of  copper 
1/2,  zinc  14,  nickel  %  and  used  for  wires  of  resist- 
ance coils. 

Girder  Armature. — An  armature  whose  core  in  shape 
resembles  a  girder  or  H. 

Glass  Fuse. — A  fuse  confined  in  a  tube  of  glass  with 
metallic  ends. 

Globe  Net  for  Arc  Lamp. — A  light  wire  netting  some- 
times used  on  the  outside  of  arc  light  globes. 

Glow  Lamp,  Electric. — A  lamp  in  which  the  light  is 
obtained  by  glow  illumination.  Another  term  ap- 
plied to  electric  incandescent  lamps. 

Gold  Bath. — An  electrolyzable  solution  of  gold  salt  used 
for  depositing  the  metal  in  the  electro-plating  pro- 
cess ;  a  gold  plate,  which  acts  as  the  anode,  being 
immersed  in  the  liquid  opposite  the  article  to  be 
plated,  and  which  article  acts  as  the  cathode. 

Gold-Leaf  Electroscope. — An  electroscope  consisting 
of  two  leaves  of  gold  enclosed  in  a  glass  vessel  and 
hung  in  contact  with  each  other  from  the  end  of  a 
conductor,  and  which  diverge  when  excited,  thus 
serving  to  detect  the  presence  of  an  electric  charge, 
or  to  determine  whether  it  is  positive  or  negative. 

Good  Earth. — Solid  earth  connection.  Total  earth  con- 
nection. A  fault  when  a  conductor  is  fully  con- 
nected to  earth  or  grounded  at  some  intermediate 
point. 


104  ELECTRICAL  DICTIONARY 

Governor,  Electric. — A  device  serving  to  control  the 
speed  of  steam  engines  and  electric  motors,  or  to 
govern  the  resistance  of  an  electric  circuit,  the 
flow  of  fluids  into  or  out  of  their  reservoirs,  the 
direction  of  a  current  in  a  plating  bath,  and  to 
perform  other  like  functions. 

Gradient. — The  rate  of  ascent  or  descent  by  regular 
degrees  of  inclination  or  quantity  as  referred  to 
some  fixed  point  or  quantity. 

Gramme. — A  unit  of  weight  equivalent  to  the  weight  of 
one  cubic  centimeter  of  pure  water  at  its  maximum 
density  at  a  temperature  of  39.2  degrees  Fahren- 
heit, in  a  vacuum.  A  unit  equal  to  15.43235  grains 
troy  or  avoirdupois  weight. 

Gramme  Armature  Winding. — A  winding  taking  its 
name  after  Gramme,  who  first  used  it  on  the 
armature  of  a  dynamo-electric  machine. 

Gramme-Calorie. — The  quantity  of  heat  which  is  nec- 
essary to  raise  a  gramme  of  water  one  degree  cen- 
tigrade. 

Gramme-Ring  Transformer. — A  transformer  the  pri- 
mary and  secondary  coils  of  which  are  placed  on 
closed  rings. 

Gramophone. — An  instrument  which  records  and  repro- 
duces articulate  speech. 

Gramophone  Record. — A  record  of  speech  -secured  by 
means  of  a  gramophone. 

Granular-Carbon  Telephone-Transmitter. — A  telephone 
transmitter  is  which  carbon  dust  is  employed. 

Graphite. — A  condition  of  carbon  distinguished  by  its 
softness  and  metallic  luster,  and  serving  to  write 
on  paper  and  other  suitable  material  surfaces. 


ELECTRICAL  DICTIONARY  105 

Graphophone. — See  Gramophone. 

Graphophone  Record. — See  gramophone  record. 

Grappling. — Recovering  a  sunken  cable  or  other  object 
with  a  grapnel. 

Grapnel. — A  device  serving  to  recover  a  sunken  cable 
or  other  object. 

Gravitation. — The  attraction  or  force  by  means  of 
which  all  bodies  or  particles  of  matter  in  the  uni- 
verse tend  towards  each  other. 

Gravity. — The  force  which  causes  the  tendency  of 
masses  or  particles  of  matter  toward  a  center  of 
attraction  or  towards  one  another. 

Gravity-Drop  Annunciator. — An  annunciator  whose 
signals  act  by  the  fall  of  a  drop  released  electric- 
ally. 

Gravity-Feed  Arc-Lamp. — An  arc  lamp  whose  upper 
or  positive  carbon  is  held  by  a  feeding  mechanism 
which  drops  it  towards  the  negative  carbon  by  the 
force  of  gravity. 

Grease-Spot  Photometer. — A  photometer  whose  disc  is 
a  piece  of  paper  upon  whose  center  a  spot  is  sat- 
urated with  melted  paraffine.  A  Bunsen  disc 
photometer. 

Ground. — A  term  applied  to  the  earth  when  used  as 
a  return  circuit. 

Ground  Circuit. — A  circuit  in  which  the  earth  acts  as 
a  part  of  the  course  through  which  the  current 
passes. 

Ground  Detector. — An  instrument  employed  in  a  cen- 
tral station  for  indicating,  by  the  brilliancy  of  a 
lamp,  the  presence  of  a  ground  in  a  system  of 
incandescent  lamp  distribution. 


106  ELECTRICAL  DICTIONARY 

Ground  Indicator. — An  instrument  which  instantly  in- 
dicates any  defect  in  the  insulation  on  a  line.  A 
detector  for  discovering  any  loss  of  insulation. 

Ground-Return. — A  term  used  generally  signifying  the 
use  of  the  ground  as  part  of  an  electric  circuit. 

Grounded  Dynamo. — A  dynamo  the  circuit  of  which 
has  been  grounded  purposely  or  by  accident. 

Grounding1. — A  term  given  in  electro-metallurgy  to  the 
preparatory  operation  in  the  process  of  burnishing. 
The  connecting  of  a  circuit  with  the  ground. 

Gutta-Percha. — A  concrete  juice  produced  by  various 
tropical  trees  and  much  valued  in  electrical  work 
for  its  high  properties  of  insulation  and  great 
resistance  to  the  destructive  agencies  when  used 
in  submerged  or  -submarine  cables. 

Guy. — A  rope,  rod,  chain  or  wire  attached  to  anything 
to  steady  and  support  it,  as  for  instance :  a  smoke 
stack,  telegraph  pole  and  similar  structures. 

Guy  Rods. — Metallic  rods  serving  as  guys. 

Guy  Wire. — A  wire  serving  as  a  guy. 

Gyration. — The  act  of  turning  or  whirling  around  a 
fixed  center. 

Gyrostat. — A  fly  wheel  whose  revolving  motion  is  gyro- 
static.  A  fly  wheel  having  a  considerable  move- 
ment of  mass,  properly  mounted  upon  pivots  within 
a  case  and  readily  transportable,  for  the  purpose 
of  indicating  the  resistance  offered  by  rotating 
bodies  to  changing  their  plane  of  rotation. 

Gyrostatic  Action  of  Dynamo  on  Ship-Board. — The 
action  which  takes  place  at  the  bearings  of  a 
dynamo  in  operation  on  a  rolling  vessel  at  sea, 
resulting  in  gyrostatic  stresses. 


ELECTRICAL  DICTIONARY  107 


H.  P. — An  abbreviation  for  horse  power. 

H-Armature  Core. — An  armature  having  a  core  resem- 
bling in  shape  the  letter  H.  An  I-armature,  girder 
or  shuttle. 

Half-Load  Efficiency. — The  efficiency  possessed  by  a 
device  when  working  under  half  load. 

Half-Shade  for  Incandescent  Lamp. — A  reflecting  shade 
conforming  in  outline  to  the  lamp  chamber,  but 
covering  only  one-half  of  it. 

Hand  Generator. — A  dynamo  or  a  telephone  magneto- 
generator  driven  by  hand. 

Hand-Hole  of  Conduit. — A  box  or  aperture  large 
enough  to  admit  the  hand  and  providing  for  access 
to  the  cable  under  ground,  thus  readily  permitting 
the  cable  to  be  tapped. 

Hand  Regulation. — Eegulation  of  a  dynamo  accom- 
plished by  the  hand,  as  distinguished  from  regula- 
tion automatically  effected,  and  which  maintains 
constant,  either  the  current  or  the  potential. 

Hand  Regulator. — A  resistance  box  the  separate  coils 
of  which  are  easily  set  within  or  removed  from  the 
circuit  by  hand. 

Hand  Telephone. — A  telephone  receiver  used  by  hold- 
ing it  in  the  hand  as  distinguished  from  one 
adjusted  to  the  head. 

Hanger  Board. — A  board  serving  to  facilitate  the 
removing  or  replacing  of  an  arc  lamp  from  a  cir- 
cuit. 

Hard-Drawn  Copper  Wire. — Copper  wire,  hardened 
without  annealing  by  being  drawn  several  times. 


108  ELECTRICAL  DICTIONARY 

Hard  Porus  Cell. — A  hard-burned  porus  cell,  which 
used  in  a  voltaic  cell  obtains  a  comparatively  high 
resistance;  but  which  has  greater  capacity  of 
resistance  against  the  disintegrating  action  of  the 
crystallizing  saline  substances  in  the  battery. 

Harmonic  Analyzer. — An  instrument  which  resolves 
automatically  a  complex  harmonic  into  its  simple 
harmonic  components.  A  receiver  containing  a 
vibrating  reed  acted  upon  by  an  electro-magnet  and 
answering  only  to  impulses  tuned  to  its  own  pitch, 
and  when  such  impulses  are  received  from  the 
magnet  the  reed  vibrates,  but  will  not  respond  to 
impulses  not  in  harmonic  frequency. 

Harmonic  Currents. — Currents  which  alternate  period- 
ically and  vary  harmonically.  Electric  currents 
that  are  harmonic  functions  of  time.  Simple 
periodic  currents  the  strengths  of  which  are  ex- 
actly represented  by  sinusoids. 

Harmonic  Frequencies. — A  succession  of  frequencies 
the  values  of  which  being  integral  multiples  of 
their  fundamental. 

Harmonics. — The  doctrine  or  science  of  musical  sounds. 
The  secondary  or  less  distinct  tones  which  accom- 
pany any  principal  and  apparently  simple  tone. 

Harveyizing. — A  process  by  which  steel  plates  are  su- 
perficially hardened. 

Haulage,  Electric. — The  moving  of  car  or  vessel  by  the 
action  of  electricity. 

Head-Board  of  Dynamo. — A  board  insulated  and  em- 
ployed on  a  dynamo-electric  machine  to  receive  ter- 
minals or  switches. 

Head-Board  of  Motor. — A  switchboard  connected  with 
and  used  to  start  a  motor. 


ELECTRICAL  DICTIONARY  109 

Head  Guy. — A  guy  made  fast  to  the  top  of  a  pole. 

Head-Light,  Electric. — An  engine  head  parabolic  reflec- 
tor illuminated  by  electricity. 

Head  of  Liquid. — The  perpendicular  distance  from  the 
level  of  a  liquid  in  a  vessel  to  the  center  of  gravity 
of  an  orifice  placed  in  it. 

Jleat. — The  force  agent  in  nature  upon  which  depends 
the  -state  of  bodies  as  solid  fluid  or  aeriform,  and 
recognized  in  its  effects  by  expansion,  fusion,  evap- 
oration, etc.  A  form  of  energy. 

Heat,  Electric. — Heat  generated  by  an  electric  current 
passing  through  a  conductor. 

Heat  Units. — Units  founded  upon  the  amount  of  heat 
necessary  to  raise  one  degree  of  the  thermometric 
scale. 

Hekto. — A  prefix  for  one  hundred. 

Hekto-Ampere. — One  hundred  amperes. 

Hekto- Watt  Hour. — One  hundred  watt-hours,  or  a  unit 
of  work  equal  thereto. 

Heliograph. — An  instrument  for  communication  by 
means  of  sunlight  flashes  which  are  made  by  their 
manipulation  to  represent  the  Morse  telegraphic  al- 
phabet. An  instrument  employed  for  communica- 
tion between  distant  points  and  effected  by  inter- 
cepting at  intervals  the  beams  reflected  from  a  mir- 
ror, the  various  durations  of  which  correspond  to 
the  Morse  signal  code. 

Heliostat. — An  instrument  by  which  a  sunbeam  may  be 
introduced  into  a  dark  room  from  a  mirror  which 
is  mounted  on  an  axis  parallel  to  the  earth's  axis, 
and  by  means  of  clock-work  the  beam  is  kept  in  a 
fixed  position  despite  the  rotation  of  the  earth. 


110  ELECTRICAL  DICTIONARY 

Heliotropism. — A  twisting  on  the  growth  of  stalks  and 
stems  resulting  from  the  influence  of  any  light 
source. 

Helix. — A  spiral  line,  as  of  wire  .in  a  coil.  A  circum- 
volution. 

Henry. — The  practical  unit  of  electro-magnetic  or  mag- 
netic inductance. 

Henry's  Coils. — A  number  of  induction  coils  separate 
and  connected  in  a  manner  so  that  the  currents  in- 
duced in  the  secondary  of  the  first  coil  results  in 
the  same  effect  in  the  secondary  of  the  second  coil, 
with  the  primary  of  which  it  forms  a  series  con- 
nection, and  thus  throughout  the  coils. 

Hermetical  Seal.— A  seal  obtained  in  a  glass  vessel  by 
heating  its  neck  until  it  is  soft  and  then  twisting  it 
until  the  aperture  is  accurately  closed. 

High  Commutator  Bars. — Commutator  bars  which  in 
the  natural  wear  of  the  commutator  project  beyond 
the  others  and  require  turning  down  to  restore 
cylindrical  symmetry. 

High-Economy  Lamp. — A  lamp  of  high  efficiency. 

High  Frequency. — A  frequency  greater  than  that  usual- 
ly employed. 

High-Potential  Current. — A  term  carelessly  used  to  sig- 
nify a  current  caused  by  high  electromotive  forces. 

High-Potential  System.— Pressure  from  300  to  3,000 
volts,  according  to  the  National  Electric  Code. 

High-Potential  Testing-  Transformer. — An  alternating 
current  transformer  which  obtains  a  high  alternat- 
ing pressure  from  an  ordinary  alternating  current 
circuit  and  employed  to  test  insulation. 


ELECTRICAL  DICTIONARY  111 

High-Potential  Wires. — Circuit  wires  highly  insulated 
and  used  for  connection  with  high  potential 
sources. 

High  Resistance. — A  much  higher  resistance  for  any 
circuit  or  apparatus  than  that  which  is  usually  em- 
ployed. 

High-Resistance  Magnet. — A  term  applied  sometimes  to 
a  long-coil  magnet  of  light  wire  and  which  pos- 
sesses high  electric  resistance. 

High-Speed  Electric  Motor. — An  electric  motor  of  the 
usual  design  as  distinguished  from  one  built  to  run 
at  low  rate  of  speed. 

High-Tension. — A  circuit  used  with  high  electric  pres- 
sures. 

High  Vacuum. — A  vacuum  approximately  or  nearly 
perfect;  a  vacuum  wherein  the  molecules  of  the 
residual  gas  seldom  come  into  collision  with  one  an- 
other in  the  containing  vessel,  but  move  to  and  fro 
between  its  walls,  the  gas  being  in  an  ultra-gaseous 
condition. 

Hissing  Arc. — A  term  applied  to  a  voltaic  arc  which 
produces  a  hissing  noise  due  to  too  close  approach 
of  the  carbons. 

Holder  for  Safety  Fuse.— A  support  of  infusable  mate- 
rial serving  to  hold  a  safety  fuse  and  catch  the 
fused  metal. 

Holders  for  Brushes  of  Dynamo-Electric  Machine. — The 

adjustable  clamps  for  holding  the  armature  brushes 
of  dynamos  and  motors. 

Holophane. — A  globe  or  chamber  of  glass  with  a  lenti- 
form  external  surface  employed  for  the  better  dif- 


112  ELECTRICAL  DICTIONARY 

fusion  of  the   light   emerging  from  the   enclosed 

source. 
Homopolar  Dynamo. — A  one-pole  dynamo.    A  dynamo 

the  conductor  of  which  moves  constantly  past  poles 

of  single  polarity  only. 
Horizontal    Candle    Power. — The    intensity    of    light 

emitted  horizontally  from  a  source. 
Horizontal  Intensity  of  Light. — The  intensity  of  light 

measured  horizontally. 

Horns  of  Pole-Pieces  of  Dynamo. — In  dynamo-electric 
machines  the  projecting  ends  of  the  pole  pieces  to- 
wards or  from  which  the  outer  uncovered  perimeter 
of  the  armature  turns  in  its  regular  operations. 

Horse-Power. — A  unit  or  standard  by  which  the  capa- 
bilities and  rate  of  doing  work  by  a  prime  mover 
is  measured ;  estimated  as  33,000  pounds  raised  one 
foot  in  a  minute. 

Horse-Power,  Electric. — A  rate  of  electrical  perform- 
ance equal  to  746  watts,  or  746  volt-coulombs  per 
second. 

Horse-Power-Hour. — A  unit  or  standard  of  work  equal 
to  that  accomplished  by  one  horse-power  during 
one  hour. 

Horseshoe  Electric  Magnet. — An  electro-magnet  the 
core  of  which  resembles  a  horseshoe  or  the  letter  U 
in  shape. 

Horseshoe  Magnet. — A  bar  of  magnetized  steel  or  hard 
iron  resembling  a  horseshoe  or  the  letter  U  in 
shape. 

Hot-Wire  Ammeter. — An  ammeter  the  readings  of 
which  are  established  by  taking  as  a  basis  the  ex- 
pansion of  a  wire,  obtained  by  an  increase  of  tern- 


ELECTRICAL  DICTIONARY  113 

perature  resulting  from  the  passage  through  it  of 
the  current  to  be  measured. 

Hot-Wire  Thermometer. — A  thermometer  which  indi- 
cates by  means  of  the  expansion  of  a  bi-metallic 
wire. 

Hot-Wire  Voltmeter. — A  voltmeter  the  indications  of 
which  are  based  upon  the  lengthening  of  a  wire  oc- 
cupying a  position  in  the  circuit  of  the  electro- 
motive force  to  be  measured. 

Hydraulic  Power  Dynamometer. — A  dynamometer  serv- 
ing to  measure  hydraulic  power. 

Hydraulic  Storage. — The  storing  of  energy  by  forcing 
water  into  elevated  reservoirs. 

Hydraulics. — That  branch  of  science  or  engineering 
which  treats  of  fluids  in  motion;  the  transmission 
of  water  through  conduits  or  pipes,  and  the  appa- 
ratus employed  in  raising  or  moving  water. 

Hydro-Dynamics. — That  branch  of  the  science  of  me- 
chanics which  relates  to  the  laws  of  rest  and  motion 
of  fluids. 

Hydrometer. — An  instrument  employed  to  determine 
the  amount  of  moisture  in  the  atmosphere. 

Hypothesis. — A  proposition  or  principle  which  is  as- 
sumed in  order  to  draw  an  inference  or  conclusion 
in  proof  of  the  point  in  question.  A  theory  as- 
sumed to  account  for  known  phenomena. 

Hypothetical. — Pertaining  to  a  hypothesis. 

Hypsometer. — An  instrument  employed  to  determine 
altitudes  by  ascertaining  the  temperature  at  which 
water  will  boil  at  such  altitudes. 

Hysteresis. — A  tardiness  of  magnetization  in  respect  to 
magnetizing  force.  Molecular  friction  proceeding 


114  ELECTRICAL  DICTIONARY 

from  magnetic  variations  of  stress.  A  quality  in- 
herent in  a  paramagnetic  substance  through  which 
energy  is  dissipated  when  its  magnetization  is  re- 
versed. 

Hysteresis  Losses. — Losses  of  useful  energy  resulting 
from  hysteresis. 

Hysteretic  Torque. — The  part  of  the  torque  of  a  dyna- 
mo-electric machine  resulting  from  hysteretic  influ- 
ence and  calling  for  the  expenditure  of  mechanical 
work  to  develop  hysteretic  energy,  as  heat  in  the 
iron  undergoing  magnetic  reversal. 


I.  H.  P. — An  abbreviation  for  indicated  horse-power. 

Idle  Coil. — A  coil  through  which  no  current  is  passing. 

Idle  Wire. — A  wire  through  which  no  current  is  passing 
*  or  no  useful  current  is  passing.  An  open-circuited 
armature  wire  which  is  not  generating  E.  M.  F. 

Igniter. — A  strip  of  carbon  inserted  between  the  free 
ends  of  a  candle  of  the  Jablochkoff  type  and  which 
upon  the  passage  of  a  current  through  it  becomes 
incandescent  and  burns  away  in  a  short  time,  thus 
.forming  an  arc  producing  the  light. 

Ignition,  Electric. — The  act  of  igniting  an  explosive  or 
any  combustible  substance  with  heat  generated  by 
electricity. 

Illuminated  Dial  Instrument. — An  instrument  used  in 
engine  rooms  or  central  stations,  the  dial  of  which 
is  translucent  and  illuminated  from  behind  in  order 
that  the  indicator  may  be  seen  distinctly  from  a 
distance. 


ELECTRICAL   DICTIONARY  115 

Illumination. — The  current  of  light  projected  on  a  sur- 
face per  unit  of  area  from  a  source  of  light  directly 
or  by  reflection,  indirectly. 

Impact. — The  single  instantaneous  blow  or  stroke  of  a 
body  in  motion  against  another  either  in  motion  or 
at  rest. 

Impedance. — The  relation  of  any  impressed  electro- 
motive force  to  the  current  which  is  produced  by  it 
in  a  conductor.  The  sum  of  all  factors  offering  re- 
sistance to  a  current,  whether  spurious  or  ohmic — 
apparent  resistance. 

Impedance  Coils. — A  name  sometimes  given  to  chok- 
ing, economy  or  reactance  coils. 

Imperfect  Magnetic  Circuit. — A  term  sometimes  given 
to  a  magnetic  circuit  in  which  the  intensity  of  the 
flux  is  greater  through  some  parts  of  the  ferric  cir- 
cuit than  through  others  by  reason  of  the  magnet- 
izing coil  being  put  only  on  one  part  of  the  core, 
hence  some  of  the  lines  of  induction  instead  of  com- 
pleting their  circuits  through  the  core  itself,  do  so 
through  the  space  surrounding  the  core. 

Impressed. — Forced  upon  or  made  to  act. 

Impressed  Electromotive  Force. — The  electromotive 
force  caused  to  act  in  a  circuit  to  generate  a  cur- 
rent in  it.  The  electromotive  force  expended  in 
causing  a  current  induction  in  a  neighboring  cir- 
cuit. 

Impulse. — The  motion  produced  by  the  sudden  or  mo- 
mentary action  of  a  force  upon  a  body. 

Impulsive  Current-Rush  in  Inductive  Circuit. — An  ab- 
normal flow  of  current  occasioned  by  the  sudden 
switching  of  a  transformer  on  to  an  active  main. 


116  ELECTRICAL  DICTIONARY 

Incandescence. — The  glowing  whiteness  of  a  body 
caused  by  intense  heat. 

Incandescent  Bombardment  Lamp. — An  incandescent 
lamp  in  which  the  molecular  bombardment  result- 
ing  from  the  passage  of  an  electric  discharge 
through  a  rarefied  space  raises  a  refractory  ma- 
terial to  a  state  of  incandescence. 

Incandescent  Circuit. — A  circuit  upon  which  incandes- 
cent lamps  are  operated. 

Incandescent-Cut-Out. — A  cut-out  adapted  to  use  in  an 
incandescent  circuit.  A  safety-fuse  cut-out. 

Incandescent  Filament. — The  filament  employed  as  a 
conductor  in  an  incandescent  lamp,  usually  of 
small  cross-section. 

Incandescent  Electric  Lamp. — An  electric  lamp  pro- 
vided with  a  filament  usually  of  carbon,  and  which 
produces  the  light  by  being  electrically  heated  to  a 
state  of  incandescence. 

Incandescent  Lamp-Cord. — A  flexible  cord  inclosing 
two  conductors  and  used  for%a  pendant  incandes- 
cent lamp. 

Incandescent  Lamp-Socket. — A  socket  serving  to  re- 
ceive and  hold  an  incandescent  lamp. 

Incandescent  Mantle-Burner. — A  gauze  mantle  made  of 
a  refractory  substance  and  raised  to  a  state  of  in- 
candescence by  the  heat  of  a  Bunsen  flame. 

Incomplete  Circuit. — A  broken  or  open  circuit. 

Indestructibility  of  Energy  or  Matter. — A  hypothesis 
which  assumes  that  matter  and  energy  are  inde- 
structible and  that  the  disappearance  of  them  from 
certain  forms  is  necessarily  followed  by  their  reap- 
pearance in  other  forms. 


ELECTRICAL  DICTIONARY  117 

India  Rubber. — A  substance  obtained  from  the  milky 
juice  of  a  tropical  tree. 

Indicating  Switch. — A  switch  which  employs  an  indi- 
cator from  which  it  can  be  ascertained  whether  the 
circuit  of  the  switch  is  open  or  closed. 

Indicator  Card. — The  card  from  the  indicator  of  a 
steam  engine  from  which  the  horse-power  is  reck- 
oned by  means  of  the  curves  of  pressure  which  are 
traced  thereon. 

Indicator,  Electric. — A  term  used  signifying  the  divers 
styles  of  devices  which  are  employed  to  indicate  by 
the  deflection  of  a  needle  or  the  sounding  of  a  bell, 
at  some  remote  point,  the  condition  of  any  electric 
circuit  and  the  strength  of  current  flowing  through 
it,  the  head  of  liquid  pressure  carried  by  a  boiler, 
the  temperature,  speed  and  general  working  of 
machinery  and  the  occurrences  incidental  thereto. 

Induced. — Caused  by  induction. 

Induced  Current. — A  current  caused  by  electro-dyna- 
mic induction. 

Induced  Current  of  Transformer. — A  term  applied  to 
the  secondary  current  of  a  transformer. 

Inducing1  Circuit. — A  circuit  causing  induction. 

Inducing  Current  of  Transformer. — A  term  used  for  the 
primary  current  of  a  transformer. 

Inducing  Magnet. — A  relay's  permanent  magnet. 

Inductance. — That  capacity  of  a  circuit  which  enables 
it  to  exercise  induction  and  create  lines  of  force. 
The  ratio  between  the  total  induction  through  a 
circuit  to  the  current  producing  it.  A  property 
by  virtue  of  which  the  passage  of  an  electric  cur- 
rent, in  producing  a  magnetic  field,  is  necessarily 


118  ELECTRICAL  DICTIONARY 

accompanied  by  an  absorption  of  electric  energy. 
A  constant  quantity  in  a  circuit  having  no  iron  and 
at  rest  and  which  is  usually  expressed  in  the  prac- 
tical units  of  induction  or  henrys. 

Induction. — The  influence  exerted  without  apparent 
communication  by  a  magnetic  field  or  a  charged 
mass  upon  neighboring  bodies. 

Induction  Alternator. — A  name  used  signifying  a  cer- 
tain type  of  alternating  generator. 

Induction  Coil. — A  coil  wherein  the  electro-motive  force 
of  a  portion  of  a  circuit  is  by  mutual  induction 
made  to  cause  higher  or  lower  electromotive  force 
in  a  neighboring  circuit. 

Induction  Generator. — A  generator  which  furnishes 
currents  that  have  been  reinforced  in  its  coils  after 
receiving  them  from  the  line  by  induction.  An 
alternating  dynamo  whose  generative  power  is  ob- 
tained by  the  inductive  action  of  the  main  current. 

Induction  Multihase-Motor. — An  alternating-current 
induction-motor  worked  by  multiphase  currents. 

Inductor  Alternator. — An  alternator  having  both  its 
armature  and  field  fixed  and  with  a  rotating  frame 
fixed  within  it,  so  as  to  generate  E.  M.  F.  in  coils 
on  the  armature. 

Inductor  Alternating  Generator. — An  alternator  in 
which  there  is  no  rotation  of  field  coils  or  armature 
coils,  and  having  a  rotating  iron  frame  which  pe- 
riodically fills  the  armature  lops  with  magnetic 
flux  and  empties  them. 

Inductor  Dynamo. — A  generator  with  stationary  field 
and  armature  coils;  the  motion  of  inductors  pass- 
ing them  altering  the  magnetic  flux  through  them. 


ELECTRICAL  DICTIONARY 

Inductor  Generators. — Inductor  alternators  or  dyna- 
mos. 

Inductors. — Laminated  masses  of  iron  in  inductor 
dynamos  used  to  effect  variations  of  magnetic  flux 
of  armature  and  core. 

Inertia. — That  property  in  matter  by  which  it  tends, 
when  at  rest  to  remain  so. 

Inflection. — The  bending  of  rays  of  light  or  radiant  en- 
ergy by  defraction  when  passing  by  a  sharp  edge. 

Influence. — A  term  used  at  times  signifying  electro- 
static induction. 

Injector. — An  instrument  employed  to  introduce  a  con- 
denser or  other  device  into  an  electric  circuit  at  a 
definite  moment  and  for  a  definite  interval  of  time. 

In-Put. — The  power  which  a  machine  absorbs  in  per- 
forming a  certain  quantity  of  work. 

Inside  Wiring. — The  conductors  employed  in  a  system 
of  incandescent  lighting  to  convey  the  current  to 
the  interior  of  a  building  which  is  to  be  lighted. 
Conductors  located  in  the  interior  of  a  building. 

Installation. — A  term  including  all  the  accessories  of 
and  the  entire  plant  necessary  for  the  performance 
of  any  specified  work. 

Installation,  Electric. — The  establishment  of  an  electric 

plant. 
Instantaneous. — Done  in  an  instant. 

Insulate. — To  insulate  a  body  in  such  manner  that  elec- 
tricity can  neither  be  conducted  to  it  nor  from  it. 

Insulated  Conductors. — Conducting  wires  covered  with 
an  insulating  coating. 

Insulating1  Joint. — A  joint  used  for  the  purpose  of  in- 


120  ELECTRICAL  DICTIONARY 

sulating  a  combination  gas  and  electric  fixture 
from  the  gas  pipe. 

Insulating  Tape. — An  adhesive  tape  of  flexible  material 
•saturated  with  rubber,  okonite  or  other  insulating 
substances  and  used  to  effect  insulation  on  the 
stripped  ends  of  wire  or  electric  conductors  at 
joints  or  wherever  else  exposed. 

Insulating  Varnish. — A  varnish  composed  of  insulating 
material. 

Insulating  Washer. — A  washer  made  of  insulating  ma- 
terial. 

Insulation. — The  application  or  employment  of  any  ma- 
terial or  medium  by  which  electricity,  heat,  light, 
etc.,  are  prevented  from  entering  into  or  escaping 
from  the  body  insulated. 

Insulation  Break-Down. — Any  defect  of  insulation 
which  prevents  or  interferes  with  perfect  insula- 
tion. 

Insulation  Resistance. — That  resistance  offered  by  an 
insulated  conductor's  insulation,  expressed  in  ohms 
per  mile  and  ascertained  by  measuring  the  resist- 
ance between  the  conductor  and  water  into  which 
a  portion  of  the  line  has  been  immersed ;  the  length 
of  the  immersed  portion  being  known  and  having 
its  ends  above  the  fluid.  The  resistance  which  ex- 
ists between  a  conductor  and  the  earth  in  a  circuit 
through  insulating  materials  which  lie  between 
them.  A  term  used  to  express  the  resistance  of  in- 
sulating material  which  covers  a  wire  or  conductor. 
Any  resistance  offered  by  insulation. 

Intake. — A  synonymous  term  for  "in-put." 

Intake  of  Dynamo. — The  mechanical  activity  taken  in 
by  a  dynamo  relatively  to  time. 


ELECTRICAL,  DICTIONARY  121 

Integrating  Meter. — A  meter  which,  records  and  reckons 

a  quantity  relatively  to  time. 
Integrating  Wattmeter. — A  meter  or  watt-hour-meter 

which    indicates    the    whole    power    that    passes 

through  it  relatively  to  time. 

Intensity. — The  amperage  or  strength  of  a  current.  The 
strength  of  a  magnetic  field  or  its  magnetic  den- 
sity as  distinguished  from  tension  in  case  of  dynam- 
ic electricity.  The  degree  of  concentrated  acting 
forces. 

Intensity  of  Current. — Current  strength.  Current 
strength  or  density  taken  per  unit-area  of  cross- 
section. 

Intensity  of  Field. — The  intensity  of  a  magnetic  field 
measured  at  any  point  by  the  force  with  which 
it  acts  on  a  unit  magnet  pole  located  at  that  point. 
That  intensity  of  field  which  acts  on  a  unit  pole 
with  a  force  of  one  dyne. 

Intensity  of  Light. — The  degree  of  energy  exerted 
with  respect  to  candle-power. 

Intensity  of  Magnetization. — A  quantity  representing 
the  intensity  of  magnetization  caused  in  a  body.  A 
quantity  representing  the  intensity  of  magnetiza- 
tion conveyed  to  a  magnetizable  body  or  substance. 
The  quantity  of  magnetism  present  or  induced  in 
a  mass  and  represented  by  the  magnetic  lines  of 
force  in  cross  sectional  area. 

Inter-Connected  Armature  Winding. — A  connection  of 
the  separated  circuits  in  a  multipolar  armature  ef- 
fected in  such  manner  as  to  provide  for  the  em- 
ployment of  a  single  pair  of  brushes  on  the  com- 
mutator. An  armature  cross-connected. 


122  ELECTRICAL  DICTIONARY 

Interior  Conduit. — A  conduit  for  the  accommodation  of 
house  wires  and  located  within  the  walls  or  in 
other  suitable  spaces  inside  of  a  house  or  build- 
ing. 

Interior-Conduit  Junction  Box. — A  box  serving,  in  an 
interior  system  of  conduits  for  the  reception  of  the 
terminals  of  feeders,  and  as  a  place  where  feeders 
and  mains  or  mains  and  branches  are  connected. 

Intermittent. — Ceasing  to  act  at  intervals.  Fluctuating. 

Intermittent  Current. — A  current  flowing  and  ceasing 
to  flow  at  intervals,  resulting  in  the  practical  pres- 
ence and  absence,  alternately,  of  electricity  from 
a  circuit. 

Intermittent  Earth. — An  intermittent  contact  of  a  tele- 
graphic or  other  line  with  the  earth,  causing  a 
fault,  and  which  is  occasioned  by  the  action  of 
wind  or  by  expansion  from  heat.  A  swinging 
earth. 

International  Ampere. — The  value  of  the  ampere  which 
was  defined  in  1893  at  Chicago  by  the  International 
Electrical  Congress.  One-tenth  of  the  absolute 
C.  G.  S.  unit  of  current  strength,  or  a  value  equal 
to  the  one-tenth  of  a  unit  in  the  C.  G.  S.  system  of 
electro-magnetic  unity  and  represented  with  prac- 
tical exactitude  by  the  unalterable  current,  which, 
when  consonant  with  certain  specifications  while 
passing  through  a  solution  of  nitrate  of  silver  in 
water,  deposits  the  metal  at  the  rate  per  second  of 
0.001118  of  a  gramme. 

International  Ohm. — The  value  of  the  ohm  which  was 
defined  in  1893  at  Chicago  by  the  International 
Electrical  Congress.  The  practical  unit  of  resist- 
ance; 10°  C.  G.  S.  electro  units.  On  ohmic  value 


ELECTRICAL  DICTIONARY  123 

equal  to  109  units  of  resistance  of  the  C.  G.  S.  sys- 
tem of  electro-magnetic  units  and  represented  by 
the  resistance  opposed  to  an  electric  current  by  a 
column  of  mercury  of  a  constant  cross  sectional 
area,  14.4521  grammes  in  quantity,  at  the  melting 
temperature  of  ice,  and  a  length  of  106.3  centi- 
metres. 

International  Volt. — The  value  of  the  volt  defined  in 
1893  at  Chicago  by  the  International  Electrical 
Congress.  An  electromotive  force,  which,  steadily 
applied  to  a  conductor  whose  resistance  is  one  in- 
ternational ohm,  will  produce  a  current  of  one  in- 
ternational ampere,  and  which  is  represented  suf- 

1 000 

ficiently  well  for  practical  use  by  -    —of  the  elec- 

1434 

tromotive  force  between  the  poles  or  electrodes  of 
the  voltaic  cell  known  as  Clark's  cell,  at  a  tempera- 
ture of  15  deg.  C.  or  59  deg.  F.,  and  prepared  ac- 
cording to  certain  specifications. 

International  Watt. — The  value  of  the  Watt  defined  in 
1893  at  Chicago  by  the  International  Electrical 
Congress.  A  value  which  is  equal  to  107  units  of 
activity  in  the  C.  G.  S.  system  and  equal  to  per- 
formance at  the  rate  of  one  jouleper-second. 

Interrupted. — Opened  or  broken. 

Interrupter. — Any  device  which  breaks  or  interrupts  a 
circuit. 

Inter-Urban  Electric  Railway. — An  electric  railway- 
running  between  neighboring  towns  or  cities. 

Inter-Urban  Telephony. — Telephonic  communication 
between  neighboring  towns  or  cities. 

Inverse  Current. — A  current  produced  in  a  conductor 
when  a  current  is  started  or  strengthened  in  a 


124  ELECTRICAL  DICTIONARY 

parallel  conductor  which  has  a  parallel  component. 
The  current  produced  in  an  induction  coil  when 
the  circuit  of  the  primary  is  making  or  completing. 

Inverted  Arc-Lamp. — An  arc  lamp  wherein  the  positive 
carbon  is  below  or  inverted  instead  of  uppermost, 
as  in  the  regular  arc  lamp. 

Inverted  Dynamo. — A  dynamo  having  its  armature 
chamber  below  the  field  magnet  coils. 

Iron-Armored  Conduit. — An  iron-covered  conduit.  A 
conduit  wherein  each  duct  is  provided  with  an  iron 
covering  or  casing. 

Iron-Clad. — Covered  with  iron. 

Iron-Clad  Armature. — A  dynamo  or  motor  armature  the 
insulating  coils  of  which  are  almost  or  completely 
surrounded  by  the  iron  of  armature  core. 

Iron-Clad  Coil. — A  magnet  which  is  iron-clad. 

Iron-Clad  Dynamo. — A  dynamo  with  an  iron-clad  arma- 
ture or  encased  in  iron. 

Iron-Clad  Electro-Magnet. — An  electro-magnet  the  mag- 
netizing coil  of  which  is  almost  completely  sur- 
rounded by  iron  to  augment  its  portative  power,  or 
its  inductance,  or  to  protect  its  magnetic  variations, 
as  the  case  may  be. 

Iron-Clad  Rheostat. — A  rheostat  with  resistance  coils 
having  an  insulation  incased  in  enamel  and  sunk 
into  a  mass  of  iron. 

Iron-Loss  in  Transformer. — The  loss  of  energy  sus- 
tained by  a  transformer  by  reason  of  magnetic 
hysterics  or  friction,  and  also  due  to  the  establish- 
ment of  eddy  or  Foucault  currents  in  iron. 

Iron  Magnet  Circuit. — A  circuit  signifying  a  ferric  cir- 
cuit. 


ELECTRICAL.  DICTIONARY  125 

Isobars. — Imaginary  lines  connecting  those  places  on 
the  earth's  surface  where  the  mean  height  of  the 
barometer  at  the  level  of  the  sea  is  the  same. 

Isolated  Electric  Lighting. — Electric  lighting  by  a  plant 
situated  on  the  premises  lighted,  in  distinction  from 
one  which  is  situated  at  a  central  station  and 
which  supplies  the  current  to  a  number  of  buildings 
or  to  the  service  of  an  extended  area. 

Isolated  Plant. — An  electric  plant  supplying  the  current 
for  lighting  a  building  or  an  assemblage  of  struc- 
tures or  buildings,  in  distinction  from  one  supply- 
ing the  current  from  a  central  station. 

Isothermal  Expansion  of  Gas. — The  expansion  of  a  gas 
while  maintaining  its  temperature  constant. 

Isothermal  Surfaces. — Surfaces  of  a  body  upon  which 
the  temperature  is  the  same  at  all  points. 

J. 

Jablochkoff  Candle. — An  arc  lamp  without  regulating 
mechanism  producing  an  arc  between  the  ends  of 
parallel  carbons  which  are  maintained  at  constant 
distance  apart  by  the  introduction  between  them 
of  a  strip  of  insulating  material. 

Jablochkoff 's  Igniter. — A  small  carbon  conductor  in 
form  of  a  strip,  being  easily  raised  to  incandescence 
by  a  current,  and  which  is  introduced  between  the 
free  ends  of  the  parallel  carbons  of  a  Jablochkoff 
candle,  thus  forming  an  arc  upon  the  passage  of 
the  current. 

Jacobi's  Law. — A  law  of  electric  motors  which  states 
that  the  maximum  work  of  a  motor  is  performed 
when  its  counter  electro-motive  force  is  equal  to 


126  ELECTRICAL  DICTIONARY 

one-half  the  electro-motive  force  expended  on  the 
motor. 

Jaws  of  Switch. — A  clamp  of  metal  used  for  the  recep- 
tion of  the  knife  blades  of  a  switch. 

Joint. — The  point  where  two  or  more  conductors  join. 

Joint  Resistance. — The  united  resistance  offered  by  a 
number  of  resistances  connected  in  parallel. 

Joule. — The  practical  C.  G.  S.  unit  of  electric  energy 
which  is  equal  to  107  ergs — 0.73734  foot  pound — 
.00134  horse-power  seconds.  The  quantity  of  elec- 
tric work  necessary  to  raise  the  potential  of  one 
coulcomb  of  electricity  one  volt.  Ten  million  ergs. 

Joule  Effect. — The  heating  effect  of  a  current  flowing 
through  a  conductor,  produced  by  its  resistance 
only. 

Joule's  Law. — A  law  stating  that  the  heating  power  of 
a  current  is  proportioned  to  the  product  of  the 
square  of  its  strength  and  the  resistance  of  the  cir- 
cuit through  which  it  flows. 

Journal. — The  portion  of  a  shaft  or  other  revolving 
piece  which  turns  in  some  other  piece  or  support. 

Jumper. — A  shunt  or  short  circuit  employed,  for  the 
time  being,  around  a  source,  lamp  or  receptive  con- 
trivance on  a  series  connected  circuit,  in  order  that 
it  may  be  easily  removed  or  repaired. 

Jump  Spark. — A  disruptive  spark  excited  between  two 
conducting  surfaces  in  distinction  from  a  spark  ex- 
cited by  a  rubbing  contact. 

Junction  Box. — A  box,  proof  against  moisture,  utilized 
in  an  underground  system  of  conductors  to  receive 
the  terminals  of  feeders,  and  wherein  the  feeders 
are  connected  to  the  main,  and  through  which  in- 
dividual consumers  are  supplied  with  currents. 


ELECTRICAL  DICTIONARY  127 

K. 

K.  W. — An  abbreviation  for  kilowatt. 

Kaolin. — A  variety  of  clay  serviceable  for  insulating. 

Keeper  of  Magnet. — A  bar  of  soft  iron  used  to  connect 
the  poles  of  a  magnet  and  designed  to  prevent  loss 
of.  magnetism,  the  magnetic  flux  passing  through  it. 

Key-Board. — A  switchboard. 

Key  Lamp-Socket. — A  lamp  socket  supplied  with  a  key 
attachment  which  is  manipulated  to  light  or  extin- 
guish the  lamp. 

Keyless. — Having  no  key. 

Keyless  Lamp-Socket. — A  lamp  socket  not  provided 
with  a  key  and  which  depends  for  its  ignition  or 
extinction  upon  a  switch  located  elsewhere. 

Keyless  Wall-Socket. — A  socket  placed  on  a  wall  for  a 
lamp  and  providing  for  the  introduction  of  a  plug 
switch. 

Kick. — A  recoil. 

Kick  of  Coil. — A  discharge  from  an  electro-magnetic 
coil. 

Kilerg. — One  thousand  ergs. 

Kilo. — A  prefix  for  one  thousand  times. 

Kilo-Ampere. — One  thousand  amperes. 

Kilo-Dyne. — One  thousand  dynes. 

Kilo-Erg. — One  thousand  ergs. 

Kilo-Gauss. — One  thousand  gausses. 

Kilogramme. — One  thousand  grammes,  equal  to  2.67951 
pounds  troy  or  2.20485  pounds  avoirdupois. 

Kilo-Henry. — One  thousand  henrys. 


128  ELECTRICAL  DICTIONARY 

Kilo- Joule. — One  thousand  joules 
Kilo- Volt. — One  thousand  volts. 
Kilo-Watt. — One  thousand  watts. 

Kilo- Watt-Hour. — The  result  in  work  equal  to  the  ex- 
penditure of  exertion  of  one  kilowatt  in  one  hour. 

Kilo- Watt  Hour  Meter. — A  wattmeter  that  records. 

Kilo-Weber. — One  thousand  webers. 

Kinetic  Theory  of  Matter. — A  hypothesis  assigning  to 
the  molecules  of  matter  the  property  of  constant 
motion  or  vibration  towards  or  from  one  another 
in  paths  lying  within  the  radii  of  their  reciprocal 
attractions  and  repulsions. 

Kinetics. — The  science  which  treats  of  motions  consid- 
ered in  themselves  or  apart  from  their  causes. 

Kinetoscope. — An  instrument  for  obtaining  the  effect 
of  a  panorama  or  moving  objects  by  a  display  of 
suitable  pictures  in  rapid  succession. 

Knife-Break  Switch.— A  knife  switch. 

Knife-Switch. — A  switch  with  narrow,  deep,  movable 
arm,  of  copper  or  brass,  which  when  making  con- 
tact is  forced  in  between  two  springs  connected  to 
one  terminal. 

Knob  Insulator. — An  insulator  in  the  form  of  a  knob 
divided  into  two  parts  and  utilized  to  support  a 
single  wire  by  being  clamped  together  with  a  sup- 
porting screw. 

Kynanizing. — A  process  used  to  preserve  telegraph  or 
railroad  timbers  by  the  introduction  of  corrosive 
sublimate  into  the  pores  of  the  wood. 


ELECTRICAL   DICTIONARY  129 


Lag. — Dropping  behind.    To  be  tardy. 

Lag  of  Motor  Brushes. — A  change  of  position  of  the 
brushes  on  a  motor's  commutator  in  a  direction  op- 
posed to  its  rotation  for  the  purpose  of  obviating 
sparking. 

Lag  of  Resultant  Flux. — In  an  induction  motor,  the  dis- 
placement in  phase  of  the  magnetic  flux  behind  the 
impressed  magneto-motive  force. 

Lagging  Electro-Motive  Force. — The  lagging  of  an  elec- 
tro-motive force,  or  component  part  thereof,  behind 
a  current  or  flux. 

Lagging  of  Current. — The  retarding  in  phase  of  an  al- 
ternating current  behind  the  pressure  which  pro- 
duces it. 

Laminated. — Made  up  of  thin  plates,  as  a  laminated 
armature  core  or  converter  core. 

Laminated  Core. — The  subdivision  of  the  core  of  an 
armature,  induction  coil  or  converter  into  plates 
insulated  more  or  less  perfectly  from  each  other  in 
order  to  prevent  the  formation  of  Foucault  cur- 
rents. 

Laminated  Magnet. — A  magnet  equipped  with  a  lami- 
nated core. 

Lamp  Base. — That  part  of  an  incandescent  lamp  cham- 
ber designed  for  the  entrance  into,  the  chamber  of 
the  leading-in  wires  and  which  is  supplied  with 
tw.o  insulated  plates  of  metal  which  are  connected 
with  the  leading-in  wires. 

Lamp  Circuit. — A  circuit  having  electric  lamps  or  lamp. 


130  ELECTRICAL  DICTIONARY 

Lamp  Cut-Out. — An  application  for  automatically  cut- 
ting a  series  connected  arc  lamp  out  of  a  circuit 
when  the  carbons  are  entirely  consumed. 

Lamp  Dimmer. — A  reactive  coil  serving  to  vary  the  in- 
tensity of  incandescent  lights  connected  with  an 
alternating  circuit.  A  resistance  coil  in  series  with 
lamps. 

Lamp  Efficiency. — Ordinarily  a  term  used  to  signify 
the  watts  consumed  by  a  lamp  per  candle  power  de- 
livered, but  more  properly  expressed  as  the  recip- 
rocal of  that,  or  the  number  of  candles  obtained 
from  an  incandescent  lamp  per  watt  supplied  to  it. 

Lamp-Hour. — A  unit  of  commercial  supply  of  electric 
force.  The  volt-coulombs  necessary  to  operate  an 
electric  lamp  for  one  hour. 

Lamp  Indicator. — An  instrument  serving  in  a  central 
station  to  indicate  the  presence  of  the  proper  volt- 
age or  potential  difference  on  the  mains.  A  lamp 
serving  on  a  telephone  switch  board  which  indi- 
cates the  calling  or  ringing  off^by  a  subscriber. 

Lamp  Rod. — A  rod  contained  in  a  common  arc  lamp 
serving  to  support  the  positive  carbon,  and  the  rods 
serving  to  support  both  carbons  in  a  focusing  lamp. 

Lap  Joint. — A  joint  in  which  the  ends  are  overlapped 
and  secured  in  place  by  riveting  or  otherwise.  A 
joint  secured  by  firmly  lapping  together  the  ends 
of  two  conducting  wires  and  then  wrapping  them 
with  a  separate  wire  or  by  soldering. 

Lap  Winding. — A  winding  for  disc  and  drum  armatures 
consisting  of  lapping  back  each  lead  of  wire  to- 
wards the  preceding  lead  upon  the  commutator  end 
of  the  armature. 


ELECTRICAL  DICTIONARY  131 

Latent. — Not  visible  or  apparent.    Hidden. 

Launch,  Electric. — A  launch,  employing  electric-motive 
power. 

Law. — The  regular  sequence  by  which  certain  phenom- 
ena or  effects  follow  certain  conditions  or  causes. 
The  uniform  relations  according  to  which  forces 
act  in  producing  effects  or  are  manifested  in 
phenomena. 

Law  of  Ohm. — The  law  which  expresses  the  relation  ex- 
isting between  current  electro-motive  force  and  re- 
sistance in  an  active  electric  circuit.  Ohm's  law. 

Law  of  Volta. — A  law  which  states  that  in  an  electro- 
chemical series  the  electro-motive  force  which  ex- 
ists between  any  two  metals  will  amount  to  the 
entire  electro-motive  force  between  all  the  metals 
which  intervene. 

Laws  of  Becquerel. — Becquerel's.law  for  the  magneto- 
optic  rotation  of  the  plane  of  polarization. 

Laws  of  Coulomb. — Laws  for  the  force  of  magnetic  at- 
traction and  repulsion  between  magnetized  bodies 
or  adjacent  magnet  poles. 

Laws  of  Faraday. — Laws  of  electrolytic  decomposition. 

Laws  of  Joule. — Laws  of  the  production  of  heat  by  the 
passage  of  an  electric  current  through  a  circuit. 

Lead. — A  conductor  which  is  insulated  and  leads  to  and 
from  a  source.  An  insulated  conductor  employed 
in  a  telegraphic  system  for  leading  to  an  instru- 
ment, circuit  battery  or  station.  A  conductor  in  a 
multiple  connected  circuit  which  is  connected  to 
the  positive  terminal  of  the  source.  An  insulated 
conductor  in  a  system  of  electric  distribution  which 
leads  to  a  main,  a  station,  source,  feeder  or  testing 
device. 


132  ELECTRICAL  DICTIONARY 

Lead  Accumulator. — A  storage  cell  formed  by  the  im- 
mersion <3f  two  leaden  plates  in  diluted  sulphuric 
acid. 

Lead  Burning. — Securing  a  junction  by  partially  fusing 
two  lead  plates  together. 

Lead-Covered  Conductors. — Insulated  conductors  en- 
cased in  lead. 

Lead  of  Brushes  of  Dynamo-Electric  Generator. — An 

augular  deflection  from  the  regular  position  in  the 
direction  of  the  armature 's  rotation  which  is  given 
to  the  brushes  on  the  commutator  for  the  purpose 
of  obviating  sparking. 

Lead  of  Brushes  of  Dynamo-Electric  Generator. — The 

angular  change  from  the  regular  position  to  one  in 
an  opposite  direction  to  the  armature's  rotation, 
made  with  the  brushes  on  an  electric-motor,  when 
the  load  is  increased,  for  the  purpose  of  obviating 
sparking. 

Leading-In  Wires. — The  wires  which  lead  into  a  build- 
ing or  structure  from  an  aerial  circuit.  The  wires 
through  which  passes  the  current  into  and  out  of 
an  incandescent  electric  lamp.  Wires  leading  a 
circuit  into  any  enclosed  space. 

Leads. — The  conductors  which  are  connected  to  a 
source's  positive  and  negative  terminals  in  a  sys- 
tem of  parallel  distribution  or  any  system  of  elec- 
tric distribution.  Conductors  through  which  the 
current  is  led  to  or  from  any  source  or  circuit. 

Leak. — Any  escape  of  energy  by  leakage. 

Leakage. — A  loss  from  leaks. 

Leakage  Drop. — The  drop  resulting  in  a  circuit  from 
leakage. 


ELECTRICAL   DICTIONARY  133 

Leakage,  Electric. — The  dissipation  by  degrees  of  a 
current  or  charge  arising  from  imperfect  insula- 
tion. 

Leakage  Flux. — That  part  of  the  field  flux  which  pro- 
duces no  useful  effect  by  reason  of  its  failure  to 
pass  through  the  armature  of  the  dynamo  or  motor. 

Left-Handed  Armature-Windings.— rA  sinistrorsal  wind- 
ing applied  to  the  core  of  armatures. 

Left-Handed  Dynamo. — A  dynamo  whose  movement  is 
counter-clockwise  when  observed  from  the  pulley 
end. 

Left-Handed  Helix. — A  sinistrorsal  helix  or  one  wound 
left-handed. 

Left-Handed  Motor.— (See  Left-Handed  Dynamo.) 

Left-Handed  Rotation. — A  sinistral  rotation.  A  rota- 
tion opposed  to  the  direction  in  which  the  hands 
of  a  clock  move. 

Left-Handed  Solenoid. — A  solenoid  whose  windings  are 
sinistrorsal  or  rising  from  left  to  right. 

Legal  Ohm. — An  ohm  whose  value  was  defined  in  1884 
by  the  Electrical  Congress  in  Paris.  The  practical 
unit  of  resistance  equal  to  the  resistance  of  a 
column  of  mercury  one  square  millimeter  in  cross 
sectional  area  and  106  centimeters  long  at  the  tem- 
perature of  0  degrees  C.  (32  degrees  F.),  as  distin- 
guished from  the  B.  A.  unit  of  resistance  ohm,  used 
previously  to  1884,  or  the  international  ohm,  de- 
fined in  1893  at  Chicago  by  the  International  Con- 
gress. 

Length  of  Spark. — The  air  space  traversed  by  a  disrup- 
tive discharge. 
Lens. — Any  transparent  substance  ground  with  two  op- 


134  ELECTRICAL  DICTIONARY 

posite  regular  curved  surfaces  and  serving  to  bring 
a  beam  or  ray  of  light  to  a  single  focus. 

Lever  Brake  for  Car. — A  style  of  car  brake  thrown  into 
action  by  means  of  a  brake  handle. 

Lever  Hook. — An  automatic  telephone  switch  hook  de- 
signed to  hang  the  receiver  on  when  not  in  use. 

Leyden  Jar. — A  form  of  static  condenser  consisting  of  a 
glass  jar  with  metallic  coatings  placed  opposite  to 
each  other  on  the  inside  and  outside  of  the  jar. 

Lichtenberg's  Dust-Figures. — Figures  produced  on  a 
surface  of  shellac  by  rubbing  over  it  the  knob  of  a 
Leyden  jar  or  other  excited  electrode  which  leaves 
upon  the  non-conducting  surface  an  electrified 
path  to  which  a  sprinkling  of  dried,  powdered  sul- 
phur and  red  lead  will  cling,  thus  forming  the  fig- 
ures. 

Life  Curve  of  Incandescent  Electric  Lamp. — A  char- 
acteristic curve  showing  the  life  of  an  incandescent 
lamp  by  the  use  of  ordina'tes  which  respectively 
represent  the  life  in  hours  and  the  candle  power  at 
constant  pressure. 

Life  of  Electric  Incandescent  Lamp. — The  number  of 
hours  that  an  incandescent  lamp  will,  when  run- 
ning under  normal  pressure,  supply  an  efficient 
light. 

Light. — The  source  of  the  illuminating  medium  by 
means  of  which  objects  are  rendered  visible  and 
distinct. 

Light  Load  of  Machine. — A  load  considerably  less  than 
the  capacity  of  a  machine. 

Lightning  Arrester. — An  appliance  serving  to  protect 


ELECTRICAL  DICTIONARY  135 

the  apparatus  in  any  electric  circuit  from  the 
damaging  effects  of  a  discharge  of  lightning. 

Lightning-Arrester  Board. — A  board  to  which  a  light- 
ning arrester  is  connected. 

Lightning  Red. — A  lightning  conductor  in  form  of  a 
rod  attached  to  the  outside  of  any  structure  to  pro- 
tect it  from  a  discharge  of  lightning  by  conducting 
the  electricity  into  the  ground. 

Lightning  Stroke. — A  discharge  of  electricity  between 
two  clouds  oppositely  charged  or  from  a  cloud  to 
the  earth. 

Limit  Switch. — A  small  switch  provided  on  an  electric 
car  connected  in  series  with  the  brake  discs,  work- 
ing automatically,  and  so  contrived  that  it  cuts  out 
the  fields  of  both  motors  when  the  breaking  cur- 
rent is  too  great.  A  switch  released  by  the  action 
of  a  clock,  thereby  cutting  off  the  supply  at  a  pre- 
determined time. 

Limiting  Distance  of  Speech. — The  distance  to  which  a 
circuit  can  be  extended  in  a  straight  line  before 
telephonic  communication  becomes  impracticable. 
The  point  to  which  a  telephone  line  may  be  ex- 
tended and  communication  successfully  maintained 
subject  to  the  electrical  conditions  of  the  circuit 
and  the  character  of  the  apparatus  provided. 

Line  Dynamometer. — A  dynamometer  serving  to  indi- 
cate whether  a  line,  in  course  of  overhead  construc- 
tion, has  been  drawn  up  to  proper  tension. 

Line  Insulator. — An  insulator  serving  to  support  an 
aerial  line. 

Line  of  Least  Sparking. — The  diameter  on  the  commu- 
tator determining  the  position  of  the  brushes  where 
sparking  is  at  its  minimum. 


136  ELECTRICAL  DICTIONARY 

Line  Reactance. — A  line  conductor's  reactance. 

Line  Section  of  Electric  Railroad. — Any  portion  of  an 
electric  railroad  line,  insulated  in  such  manner 
from  other  parts  as  to  allow  the  separate  control 
of  the  supply  of  electric  power. 

Lines  of  Electrostatic-Force. — Lines  of  force  assumed 
to  be  present  in  an  electrostatic  field  of  force  and 
to  which  they  give  existence.  Lines  whose  pro- 
longation is  in  the  direction  in  which  the  force  of 
electrostatic  attraction  or  repulsion  acts. 

Lines  of  Magnetic-Force. — Lines  of  force  which  indi- 
cate the  distribution  of  magnetic-force.  Lines  of 
force  whose  prolongation  is  in  the  direction  in 
which  the  force  of  magnetic  attraction  or  repul- 
sion acts. 

Line-Man. — A  person  who  erects  and  keeps  line  circuits 
in  repair  and  cares  for  the  attending  equipment. 

Link-Fuse. — A  plate  of  fusible  metal  in  the  shape  of  a 
link,  employed  as  a  safety  fuse,  the  ends  of  which 
are  suitable  for  connecting  copper  fuse-wire  ter- 
minals. 

Link-Fuse  Cut-Out. — A  cut-out  using  a  link  fuse. 

Liquid  Compass. — A  style  of  compass  for  ships,  the 
needle  of  which  is  suspended  not  only  by  gimbals, 
but  is  also  contrived  in  a  manner  which  provides 
for  the  checking  of  its  oscillations  by  a  surround- 
ing liquid. 

Liquid  Flow. — The  amount  of  liquid  escaping  from  an 
opening  or  passing  through  the  cross-section  of  a 
pipe  or  conduit  in  a  specified  time. 

Liquid  Resistance  Load. — An  artificial  load  for  a  dy- 
namo consisting  of  a  quantity  of  liquid,  usually 
salt  brine,  placed  between  suitable  electrodes. 


ELECTRICAL   DICTIONARY  137 


Liquefaction. — The  conversion  of  a  solid  into  a  liquid 
by  the  sole  agency  of  heat;  or  in  the  case  of  gas, 
by  the  abstraction  of  heat  or  by  the  combined 
effect  of  pressure  and  low  temperature. 

Listening  Cam. — A  form  of  switch  employed  in  a  tele- 
phone exchange  to  connect  the  operator's  tele- 
phone with  a  subscriber's  line. 

Lithanode. — A  block  of  compressed  lead  binoxide,  with 
platinum  connecting  foils  employed  as  an  electrode 
in  a  storage  battery. 

Live  Wire. — A  wire  through  which  a  current  is  flowing. 
A  wire  connected  with  a  source  of  electric  power. 

Load. — The  work  required  of  a  machine.  The  amperes 
of  current  delivered  by  a  dynamo  under  any  given 
conditions. 

Load-Diagram  of  Station. — A  curve  representing  the 
expenditure  of  current  from  a  station  for  any 
given  length  of  time. 

Load-Factor. — The  relation  of  the  average  to  the  maxi- 
mum load. 

Loadstone. — (See  Lodestone.) 

Local  Action  of  Dynamo-Electric  Machine. — The  loss 
of  energy  sustained  by  a  dynamo  resulting  from 
the  establishment  of  eddy  currents  in  its  core,  pole 
pieces  and  other  conducting  bodies. 

Local  Battery. — A  battery  which  supplies  a  local  cir- 
cuit in  telegraphy,  where  it  is  principally  used ;  the 
battery  being  thrown  in  and  out  of  action  by  a 
relay;  its  current  performing  the  work  of  actu- 
ating the  sounder  and  any  other  local  or  station 
instrument. 

Local  Currents. — Currents  within  the  metal  parts  of  a 


138  ELECTRICAL  DICTIONARY 

dynamo.  A  term  sometimes  applied  to  Foucault 
currents. 

Lock,  Electric. — A  lock  which,  by  means  of  a  distant 
push  button,  is  automatically  released. 

Locomotive,  Electric. — A  locomotive  driven  by  elec- 
tricity, or  whose  motive  power  is  electricity. 

Locomotive  Head-Light,  Electric. — (See  Head-Light, 
Electric.) 

Lodestone. — Magnetic  magnetite  or  naturally  magne- 
tized iron  ore. 

Log,  Electric. — A  device  for  electrically  measuring  the 
speed  or  the  distance  traversed  by  ships. 

Logarithm. — The  power  to  which  a  given  invariable 
number  called  the  base  must  be  raised  in  order 
to  produce  that  number. 

Logarithmic  Curve. — A  curve  in  which  the  ordinate's 
rate  of  increase  or  decrease  is  proportionate  to  it- 
self. 

Long-Arc  System  of  Electric  Lighting. — A  system  of 
lighting  in.  which  long-arcs  are  used  requiring  high 
electro-motive  forces. 

Long-Connection  Armature- Winding. — A  connection  of 
a  two-circuit  armature-winding  effected  in  a  man- 
ner to  produce  electro-motive  forces  in  each  cir- 
cuit by  field  poles  of  one  polarity  only. 

Long  Connection  of  Two-Circuit  Gramme- Windings. — 
A  style  of  gramme-winding  wherein  the  two  cir- 
cuits from  brush  to  brush  comprise  conductors 
which  are  influenced  by  one-half  the  poles  only. 

Long-Core  Electro-Magnet. — An  electro-magnet  having 
a  long  core. 

Long-Distance  Carbon  Telephone  Transmitter. — A  tele- 


ELECTRICAL  DICTIONARY  139 

phone  transmitter  of  microphonic   character  em- 
ployed on  long  distance  lines. 

Long-Distance  Telephone  Cabinet. — A  closed  cabinet 
designed  to  exclude  external  noises  and  insure 
secrecy  in  telephonic  communications. 

Long-Shunt  Compound-Wound  Dynamo-Electric  Ma- 
chine.— A  dynamo,  compound  wound,  and  with  its 
shunt-field  magnet  coils  forming  a  shunt  to  the 
binding  posts  of  the  machine. 

Loop-Circuit. — A  term  used  sometimes  for  a  circuit  in 
multiple  or  parallel  arc.  A  circuit  having  one 
wire  going  out  and  the  other  returning,  thus  dis- 
tinguishing it  from  an  earth-return  circuit. 

Loop-Switch. — A  switch  employed  to  open  or  close  a 
loop  or  for  throwing  it  out  of  or  into  a  main  cir- 
cuit. A  switch  employed  to  connect  a  branch  office 
with  a  duplex  or  quadruplex  switch  at  a  main 
office,  thus  enabling  messages  to  be  sent  and  re- 
ceived on  the  duplex  or  quadruplex  system. 

Loop-System  of  Parallel  Distribution. — A  system  pro- 
viding for  the  connection  of  two  mains  to  a  gen- 
erator in  a  manner  intended  to  equalize  the  drop 
or  pressure,  and  effected  by  connecting  one  main 
directly  to  the  generator  at  the  home  end,  and 
connecting  the  other,  by  a  separate  wire,  at  its  dis- 
tant end,  to  the  generator. 

Loop  Winding. — A  term  applied  to  lap  winding. 

Loop-Winding  of  Alternator. — An  alternator  armature- 
winding  which  provides  for  the  laying  of  the  wire 
in  loops  on  the  outside  of  the  armature  core. 

Loose  Carbon  Transmitter. — A  telephone  transmitter  in 
which  loose  carbon  is  used. 


140  ELECTRICAL  DICTIONARY 

Loose  Contact. — A  contact  formed  by  two  or  several 
•surfaces  reposing  one  upon  another  loosely  or  em- 
ploying their  weight  only.  A  poor  contact. 

Loud-Speaking  Telephone. — A  term  used  to  designate 
a  telephone  characterized  by  the  intensity  of  sound 
emitted  by  its  receiver. 

Loudness. — The  degree  of  intensity  of  sound  corre- 
sponding to  the  amplitude  of  vibration. 

Low-Frequency. — A  frequency  of  not  many  alterna- 
tions comparatively,  per  second. 

Low-Potential  Current. — A  term  applied  at  times  to  a 
current  or  low  pressure  circuit. 

Low-Potential  System. — Less  than  300  volts ;  according 
to  the  National  Electric  Code. 

Low-Resistance  Magnet. — A  magnet  having  low  resist- 
ance magnet  coils. 

Low-Speed  Electric  Motor. — An  electric  motor  con- 
structed to  run  at  low  speeds. 

Low  Tension. — Another  term  for  low  pressure. 

Lubrication. — The  act  of  making  slippery  for  the  pur- 
pose of  reducing  friction  between  surfaces.  Inter- 
posing a  thin  film  of  material  between  two  sliding 
surfaces. 

Luminescence. — The  power  which  is  to  a  certain  degree 
possessed  by  some  bodies  for  giving  out  light,  pre- 
viously acquired  by  them,  through  exposure  to 
radiant  energy  or  light. 

Luminosity. — The  quality    of    being  luminous,   and   a 

term  sometimes  applied  to  a  source. 
Luminous  Absorption. — The   absorption  by  bodies   of 

luminous  energy  in  its  passage  through  them. 


ELECTRICAL   DICTIONARY  141 

Luminous  Efficiency. — The  relation  which  the  luminous 
radiation  given  out  by  a  source,  bears  to  the  whole 
radiant  energy  that  such  source  emits  in  a  specified 
time. 

Luminous  Heat. — The  radiation  of  heat  attended  by 
physiologically  effective  frequencies. 

Lux. — A  standard  for  illumination  in  distinction  to  il- 
luminating power.  A  unit  of  illumination  equal 
to  the  light  projected  on  each  square  metre  of  the 
inside  of  a  sphere,  the  radius  of  which  is  one  metre 
from  a  bougie  decimale  situated  at  its  center. 
The  normal  illumination  which  one  carcel  will  pro- 
duce at  the  distance  of  one  metre. 


M. 

Magnet. — A  substance  which  possesses  the  power  of 
attracting  iron  ©r  of  producing  magnetic  flux.  A 
mass  or  body  which  has  the  property  of  attraction 
for  the  opposite  pole  in  another  magnet  or  of  re- 
pelling the  like  pole  or  of  inducing  magnetism  in 
bodies  susceptible  to  magnetization. 

Magnet  Coil. — A  coil  of  insulated  wire  which  surrounds 
the  core  of  an  electro-magnet  and  through  which 
the  magnetizing  current  flows. 

Magnet  Cores. — The  bar  or  mass  of  iron  wound  with 
insulated  wire,  which  produces  an  electro-magnet 
by  the  passage  of  the  magnetizing  current. 

Magnetic  Adherence. — A  tendency  noticeable  in  bodies 
of  iron  to  adhere  to  the  poles  of  a  magnet. 

Magnetic  Attraction. — The  attraction  of  unlike  mag- 
netic poles  for  each  other. 


142  ELECTRICAL  DICTIONARY 

Magnetic  Axis. — The  line  which  connects  the  poles  of 
a  magnet. 

Magnetic  Battery. — A  term  applied  to  a  compound  per- 
manent magnet,  constructed  by  clamping  to  single 
iron  pole  pieces  a  number  of  single  permanent 
magnets. 

Magnetic  Belting. — A  belting  which  provides  for  the 
riveting  of  strips  of  sheet  iron  on  the  belt  which, 
by  reason  of  the  iron  driving  pulley  being  mag- 
netized, the  friction  or  grip  upon  the  pulley  is  in- 
creased by  attraction. 

Magnetic  Blow-Out. — A  device  employed  to  extinguish 
an  arc  by  means  of  the  flux  produced  by  an  electro- 
magnet. 

Magnetic  Blow-Out  Lightning-Arrester. — A  lightning 
arrester  in  which,  by  the  action  of  the  flux  of  an 
electro-magnet  placed  in  the  circuit  of  an  arc,  the 
arc  when  formed  is  extinguished. 

Magnetic  Circuit. — The  course  along  which  magnetic 
flux  passes. 

Magnetic  Circuit-Breaker. — A  circuit  breaker  whose 
action  is  produced  by  an  electro-magnet. 

Magnetic  Circuit- Closer. — A  circuit  closer  whose  action 
is  produced  by  an  electro-magnet. 

Magnetic  Closed-Circuit. — A  circuit  possessing  the 
magnetic  polarity  of  iron.  r- 

Magnetic  Clutch. — A  clutch  in  which  to  obtain  the  fric- 
tion required,  magnetic  attraction  is  substituted 
for  mechanical  force. 

Magnetic  Concentration. — The  freeing  of  ores  from 
their  metals  by  magnetic  attraction. 

Magnetic   Curves. — The    representation    of    magnetic 


ELECTRICAL  DICTIONARY  143 

lines  of  force  on  a  sheet  of  paper  which  has  been 

sprinkled  with  iron  filings,  and  obtained  by  gently 

agitating  the  paper  and  holding  it  in  the  magnetic 

field. 
Magnetic  Declination. — The  angular  deflection  of  the 

magnetic  needle  causing  it  to  rest  at  an  angle  with 

the  true  meridian. 
Magnetic  Density. — That  strength  of  magnetism  which 

is  represented  by  lines  of  force  per  stated  area  of 

cross  section  in  a  plane  at  right  angles  to  the  lines 

of  force. 
Magnetic  Dip. — A  deviation  from  the  horizontal  by  a 

magnetic  needle  moving  in  the  vertical  plane. 
Magnetic  Divining  Rod. — A  small  dipping  needle  used 

to  locate  the  approximate  position  of  iron  ore  in 

the  earth. 
Magnetic  Equator. — A  location  on  the  earth's  surface 

where  the  magnetic  needle  maintains  its  horizontal 

position.     A   line,    approximately   stated,    equally 

distant  from  the  magnetic  poles  of  the  earth.    The 

aclinic  line. 

Magnetic  Explorer. — A  small  coil  of  insulated  wire  em- 
ployed to  ascertain  the  position  and  extent  of  the 
magnetic  leakage  of  a  dynamo  or  other  electric 
machine,  and  used  in  connection  with  the  circuit 
of  a  galvanometer  or  telephone. 

Magnetic  Fatigue. — The  increase  in  the  hysteretic  co- 
efficient of  iron  resulting  from  an  assumed  fatigue 
following  numerous  cyclic  reversals. 

Magnetic  Fatigue  of  Transformer. — The  augmented 
hysteretic  loss  of  a  transformer. 

Magnetic  Figures. — The   grouping  of  iron  filings   ol> 


144  ELECTRICAL  DICTIONARY 

tained  upon  paper  or  glass  held  near  magnetic 
poles. 

Magnetic  Flux. — Magnetic  induction.  The  total  lines 
of  force  which  flow  through  any  magnetic  circuit. 

Magnetic  Force. — The  forces  of  attraction  and  repul- 
sion which  a  magnet  exercises;  by  some  theories 
identical  with  the  forces  of  attraction  and  repul- 
sion of  electric  currents. 

Magnetic  Friction. — The  damping  effect  which  prox- 
imity to  a  magnet  causes  to  the  movements  of  a 
body  of  metal. 

Magnetic  Fringe  at  Edge  of  Dynamo  Pole  Piece. — A 
lateral  diffusion  of  magnetic  flux  forming  the  out- 
lying edge  of  a  magnetic  field,  or  an  apparent 
fringe  of  magnetic  flux  in  the  air  around  the  poles. 

Magnetic  Gearing. — A  species  of  friction  gearing  in 
which  magnetic  adhesion  is  utilized. 

Magnetic  Hysteresis. — A  molecular  friction  resulting 
from  magnetic  change  of  stress.  Magnetization 
which  lags  behind  the  magnetizing  force.  A  qual- 
ity of  a  magnetic  substance  which  is  the  occasion 
of  the  absorption  of  energy  upon  the  reversal  of 
its  magnetization. 

Magnet  Induction. — The  strength  of  magnetism  which 
is  in  an  induced  magnet,  caused  partly  by  the 
polarized  particles  of  material  which  surround  it 
and  partly  by  the  magnetic  field.  The  density,  in 
air,  of  magnetic  force;  and  in  all  magnetic  ma- 
terials it  is  the  sum  of  the  magnetic  force  and 
the  magnetic  flux  produced  in  the  iron  there- 
by. Total  density  of  magnetic  flux.  Magnetiza- 
tion induced  in  a  magnetizable  substance  when 
brought  into  magnetic  flux. 


ELECTRICAL  DICTIONARY  145 

Magnetic  Inertia. — The  lack  of  power  of  a  magnetic 
core  to  acquire  or  to  part  with  its  magnetism  in- 
stantly. 

Magnetic  Intensity. — The  intensity  of  the  magnetiza- 
tion of  a  body  determined  by  the  magnetic  lines 
of  force  passing  through  a  unit  area  of  the  body, 
the  area  being  at  right  angles  to  the  direction  of 
force. 

Magnetic  Joint. — A  joint  made  between  adjacent  pieces 
of  iron  forming  parts  of  a  magnetic  circuit. 

Magnetic  Lag. — The  tendency  of  a  mass  of  iron  to  take 
up  magnetism  slowly.  The  tendency  of  an  iron 
core  to  resist  magnetization  resulting  in  retarda- 
tion. Magnetic  retardation. 

Magnetic  Lightning-Arrester. — Any  lightning  arrester 
using  an  electro-magnet.  An  electric-magnetic 
blow-out  arrester. 

Magnetic  Limit. — The  temperature  above  which  a  mag- 
netic substance  cannot  be  magnetized. 

Magnetic  Lines  of  Force. — Lines  along  which  a  free 
magnetic  pole  would  be  impelled.  Lines  of  force 
indicating  the  distribution  of  magnetic  force. 
Flux  paths. 

Magnetic  Needle. — A  needle  or  slender  rod  magnetized. 
A  magnetized  bar  of  steel  with  a  slight  depression 
at  its  center  which  permits  of  its  being  poised  upon 
a  sharp  pin  so  as  to  freely  rotate  or  oscillate  in  a 
horizontal  plane ;  sometimes  so  pivoted  above  and 
below  at  its  center  as  to  enable  it  to  move  freely 
in  both  vertical  or  horizontal  planes. 

Magnetic  North. — The  point  of  the  horizon  to  which 
the  north-seeking  pole  of  a  magnet  points. 


146  ELECTRICAL  DICTIONARY 

Magnet  Permeability.— The  specific  susceptibility  of 
any  mass  to  magnetization.  Magnetic  inductive 
capacity. 

Magnetic  Polarity. — Polarity  acquired  by  a  magnetiza- 
ble substance  from  magnetic  flux  when  subjected 
to  its  influence. 

Magnetic  Poles. — Those  members  of  a  magnetic  source 
at  which  the  flux  enters  or  leaves. 

Magnetic  Potential.— The  potential  at  any  point  of  a 
magnetic  field  is  the  work  which  would  be  done 
by  the  magnetic  forces  of  the  field  upon  a  positive 
unit  of  magnetism  as  it  moves  from  that  point  to 
an  infinite  distance. 

Magnetic  Repulsion. — Repulsion  reciprocally  exerted 
between  like  magnet  poles. 

Magnet  Retentivity. — The  resistance  offered  by  a  body 
to  any  variation  of  magnetization.  The  property 
of  iron  or  other  magnetic  substance  by  which  it 
slowly  receives  and  parts  with  a  magnetic  con- 
dition. Hysteretic  retention 'of  magnetism  after 
the  magnetizing  force  has  been  withdrawn. 

Magnetic  Saturation. — The  maximum  magnetic  force 
which  can  be  permanently  imparted  to  a  magnetic 
substance. 

Magnetic  Screen. — A  box  of  soft  iron,  whose  sides  are 
as  thick  as  practicable,  serving  to  protect  bodies 
within  it  from  the  action  of  a  magnetic  field  ex- 
ternal to  it. 

Magnetic  Shield  for  Watches. — An  iron  case  for  the 
reception  of  a  watch  and  serving  to  shield  it  from 
the  influence  of  external  magnetic  flux. 

Magnetic  Sounds. — Small  sharp  sounds  attending  the 


ELECTRICAL  DICTIONARY  147 

magnetization  and  demagnetization  of  easily  mag- 
netizable substances.  The  hum  of  a  transformer. 

Magnetic  Sticking  of  Armature. — The  adhesion  of  an 
armature  to  the  magnet  poles  caused  by  hysteresis. 

Magnetic  Stress. — The  stress  which  magnetic  lines  of 
force  produce  on  substances  which  they  flow 
through.  That  quality  of  flux  by  virtue  of  which 
magnetic  strain  is  produced  in  bodies  subjected  to 
its  influence. 

Magnetic-Vane  Ammeter. — An  ammeter  in  which  a 
fixed  plate  of  soft  iron  is  placed  within  the  coil, 
having  freedom  to  move  or  serving  as  an  axis,  so 
that  when  the  field  is  excited  the  two  repel  each 
other  like  polarity  being  induced  in  each,  and 
the  motion  of  the  movable  soft  iron  indicates  the 
strength  of  the  current. 

Magnetic- Vane  Voltmeter. — A  magnetic  vane  wound 
for  high  resistance. 

Magnetic  Voltmeter. — An  instrument  wherein  a  mova- 
ble needle  is  deflected  against  the  action  of  the 
field  of  a  magnet  by  the  magnetic  field  of  a  current 
proportional  to  the  difference  of  the  potential  to 
be  determined. 

Magnetization  by  Touch. — A  method  of  magnetizing  by 
applying  the  poles  of  the  inducing  magnet  to  the 
substance  to  be  magnetized. 

Magnetize. — To  impart  magnetic  properties  to  a  mag- 
netizable substance. 

Magneto. — An  abbreviation  for  magneto-electric  gener- 
ator. 

Magneto-Blasting  Machine. — A  magneto-electric  ma- 
chine serving  to  generate  the  currents  employed  in 
blasting  by  means  of  electricity. 


148  ELECTRICAL  DICTIONARY 

Magneto  Call-bell. — A  call  bell  principally  used  in  tele- 
phone systems  and  operated  by  a  current  from  a 
magneto-electric  generator. 

Magneto-Dynamics. — The  branch  of  dynamics  which 
treats  of  the  reciprocal  influence  of  magnet  poles, 

Magneto-Electric  Alternating  Machine. — An  alternator 
the  field  flux  of  which  is  produced  by  permanent 
magnets. 

Magneto-Electric  Machine. — A  magneto-generator. 

Magneto- Generator. — A  dynamo  electric  machine  the 
field  flux  of  which  is  produced  by  permanent  mag- 
nets. 

Magnetophone. — A  form  of  magnetic  siren  which  pro- 
duces sounds  in  a  telephone  by  means  of  periodic 
currents  in  its  coils  produced  by  a  perforated  disc 
of  metal  rotating  in  a  magnetic  field.  The  "Busy" 
signal. 

Magneto-Telephone  Transmitter. — A  transmitter  con- 
sisting of  a  strong  compound  magnet  having  a  coil 
of  insulated  wire  fixed  in  front  of  one  of  its  poles 
and  an  iron  core  constituting  the  pole  piece  of  the 
magnet. 

Magneto-Therapy. — Asserted  claims  of  electro-thera- 
peutic effects  obtained  by  applying  magnets  to  the 
human  body. 

Magnet  Wire. — Insulated  wire  ordinarily  cotton-cov- 
ered, serviceable  for  winding  magnets. 

Main-Circuit  Fuse. — A  safety  fuse  employed  in  a  main 
circuit  for  its  protection. 

Main-Circuit  Switch. — A  switch  introduced  into  a  main 
circuit. 


ELECTRICAL   DICTIONARY  149 

Main  Cut-Out, — A  cut-out  introduced  into  the  circuit 
of  a  main. 

Main-Feeder. — The  main  feeder  in  a  district.  The 
feeder  with  which  is  connected  the  standard  pres- 
sure indicator  by  whose  pressure  that,  at  the  end! 
of  all  the  other  feeders,  is  controlled. 

Main-Line  Cut-Out. — (See  Main  Cut-Out.) 

Main  Switch. — A  switch  which  is  connected  to  the 
electric  mains.  The  main  switch  which  controls 
a  group  of  auxiliary  switches. 

Mains. — The  parallel  conductors  which  in  a  parallel 
system  of  distribution  carry  the  main  current  and 
to  which  devices  for  transferring  are  connected. 

Make. — To  complete  a  circuit  or  close  it. 

Make-and-Break. — To  complete  and  open  a  circuit  al- 
ternately. 

Man-Hole  of  Conduit. — An  opening  in  the  surface  of 
the  road  bed,  large  enough  to  admit  a  man,  and 
communicating  with  an  underground  conduit. 

Man-Power. — A  unit  of  power  represented  by  about  75 
Watts  and  equal  to  the  one-tenth  of  a  horse  power. 

Marconi  Rays. — Electro-magnetic  rays  used  in  Mar- 
coni's system  of  wireless  telegraphy. 

Marine  Galvanometer. — A  Thompson's  galvanometer 
of  the  reflecting  type  employed  on  shipboard,  the 
needle  of  which  is  enclosed  in  a  heavy  iron  box 
to  shield  it  from  the  motion  of  magnetized  masses 
of  iron  which  otherwise  would  disturb  the  reading 
of  the  instrument. 

Mariner's  Compass. — A  compass  so  mounted  as  to  be 
suitable  for  use  on  shipboard. 


150  ELECTRICAL  DICTIONARY 

Marked  End  of  Magnet. — A  term  formerly  employed 
to  indicate  the  north-seeking  pole  of  a  magnet. 

Marked  Pole  of  Magnet. — A  term  sometimes  used  for 
the  north-seeking  pole  of  a  magnet. 

Mass. — A  body  of  matter  concreted,  assembled  or 
formed  into  a  lump.  The  quantity  of  matter  which 
a  body  contains. 

Mass,  Electric. — A  term  signifying  quantity  of  elec- 
tricity ;  the  unit  mass  representing  such  a  quantity 
as  will  operate  at  unit  distance  with  unit  force. 

Mass  Specific  Resistance. — The  resistance  offered  by 
the  known  mass  of  a  material,  viz. :  one  gramme, 
in  the  form  of  a  circular  sectional  wire  one  metre 
long. 

Master  Clock. — A  central  clock,  in  a  system  of  time 
distribution,  which  transmits  the  time  of  the  sub- 
ordinate clocks  in  its  circuit. 

Matt. — A  term  used  in  electro-plating  and  signifying 
the  appearance  of  the  deposit  of  metal  which  is 
interlaced  and  compactly  massed  in  an  electro- 
plating of  silver. 

Matter. — That  of  which  the  sensible  universe  and  all 
existent  bodies  are  composed,  which  has  three  di- 
mensions and  is  perceptible  to  the  senses. 

Maximum. — Having  the  greatest  value.  A  value 
greater  than  any  which  precedes  or  follows  it  in 
a  succession  of  values. 

Maximum  Activity  of  Motor. — The  rate  of  doing  work 
at  the  greatest  possible  capacity,  or  the  activity 
developed  when  the  useful  work  performed  is 
equal  to  one-half  the  energy  expended.  The  maxi- 
mum activity. 


ELECTRICAL  DICTIONARY  151 

Maximum  Horizontal  Intensity  of  Light. — The  greatest 
intensity  of  light  emitted  horizontally  by  a  source. 

Maximum  Magnetization. — A  term  at  times  applied  to 
the  greatest  magnetic  saturation. 

Maximum  Starting-Current  of  Motor. — The  greatest 
value  attained  by  the  starting  current  of  a  motor. 

Mean. — Average.  Having  an  intermediate  value  be- 
tween two  extremes. 

Mean  Annual  Station-Current. — The  average  current 
which  a  station  delivers  during  a  year. 

Mean  Current. — Time  average  of  current  strength.  The 
time  average  of  current  strength,  in  an  alternating 
current  circuit,  without  respect  to  sine  or  direc- 
tion. 

Mean  Electro-Motive  Force. — Time  average  of  electro- 
motive force.  The  time  average  of  the  E.  M.  F.  in 
an  alternating  current  circuit  without  respect  to 
sine  or  direction. 

Mean  Horizontal  Intensity  of  Light. — The  average 
intensity  of  light  in  the  horizontal  plane  of  the 
source. 

Mean  Spherical  Candle-Power. — An  average  candle- 
power  equal  numerically  to  the  whole  quantity  of 
light  given  out  by  a  point  source  divided  by  12, 
566.  The  average  candle-power  of  a  source  of 
light  given  out  in  all  directions. 

Measurements,  Electric. — The  determinations  of  the 
values  of  quantities  as  applied  to  electro-motive 
force,  capacity,  resistance,  energy,  etc.,  in  an  elec- 
tric circuit  or  instrument. 

Mechanical  Air  Pump. — A  mechanical  device  by  means 


152  ELECTRICAL  DICTIONARY 

of  which  the  air  is  exhausted  from,  or  compressed 
into,  any  vessel. 

Mechanical  Characteristic  of  Motor. — A  term  at  times 
used  to  signify  the  torque  and  speed  of  a  motor 
as  co-ordinates. 

Mechanical  Equivalent  of  Heat. — The  mechanical 
energy  corresponding  to  a  given  quantity  of  heat 
energy  or  the  equivalent  of  mechanical  energy  in 
heat  which  would  be  necessary  to  raise  the  tem- 
perature of  a  unit  mass  of  water  to  one  degree 
Fahr. 

Mechanical  Friction  of  Dynamo. — The  frictions  of  the 
brush,  journals  and  air  of  a  dynamo. 

Mechanical  Work. — The  action  of  force  through  space 
against  resistance.  The  expenditure  of  energy 
necessary  to  effect  a  change  in  the  external  form 
of  any  material  mass. 

Medical  Battery. — A  medical  induction  coil. 

Medical  Induction-Coil. — An  induction  coil  employed 
in  electro-therapeutics. 

Meg  or  Mega. — A  prefix  meaning  one  million  times. 

Mega-Dyne. — One  million  dynes. 

Mega- Joule. — One  million  joules. 

Mega-Lines. — One  million  lines. 

Mega- Volt. — One  million  volts. 

Mega- Weber. — One  million  webers. 

Megerg. — One  million  ergs. 

Megohm. — One  million  ohms. 

Megohm  Box. — A  box  offering  a  resistance  equal  to  one 
million  ohms. 


ELECTRICAL  DICTIONARY  153 

Mercurial  Air-Pump. — An  air  pump  operated  by  mer- 
cury to  obtain  high  vacuum;  used  largely  for  ex- 
hausting incandescent  lamp  chambers.  The  Spren- 
gel  or  Giessler  air  pumps. 

Mercurial  Connection. — A  style  of  easily  adjustable 
connection  accomplished  by  supplying  the  poles  of 
one  piece  of  apparatus  with  cavities  containing 
mercury  into  which  the  terminals  of  another  piece 
of  apparatus  are  immersed,  so  that  they  may  be 
placed  in  circuit  with  each  other. 

Mercurial  Contact. — An  electric  contact  obtained  by 
means  of  mercury. 

Mercury  Cup. — A  cup  containing  mercury  and  serving 
as  a  mercurial  contact. 

Mercury  Gauge. — A  vacuum  gauge  which  depends 
upon  the  height  of  a  mercury  column  for  its  in- 
dications. 

Mercury  Tube. — A  glass  tube,  sealed  and  containing 
mercury  so  arranged  as  to  give  out  fluorescent 
light  when  shaken. 

Metal-Cased  Blake  Transmitter. — A  transmitter  pro- 
vided with  a  sheath  of  metal. 

Metallic  Arc. — An  arc  which  forms  between  metallic 
electrodes. 

Metallic  Circuit. — A  circuit  composed  wholly  of  metal 
and  thereby  distinguished  from  an  earth-return 
circuit. 

Metallic  Conductor. — A  circuit  composed  of  metal. 

Metallic  Electrolysis. — A  mode  of  cataphoretic  treat- 
ment effected  by  making  a  contact  of  the  part  to 
be  treated  with  a  metallic  electrode  connected  to 
the  positive  pole  of  a  continuous  current  source, 


154  ELECTRICAL  DICTIONARY 

while  the  negative  pole  is  brought  into  contact 
with  some  other  part  of  the  body,  thus  driving 
cataphoretically  the  metallic  salts,  formed  by  elec- 
trolysis at  the  anode,  into  the  tissues  beneath  the 
electrode. 

Metallic  Filament. — A  metallic  wire  used  in  an  incan- 
descent lamp  as  a  filament. 

Metallic  Resistance. — A  term  at  times  employed  to  sig- 
nify the  resistance  of  wires  or  conductors  as  op- 
posed to  the  resistance  of  insulating  materials. 

Metallic  Solution. — A  solution  of  metallic  salt. 

Metallo-Chromes. — A  name  by  which  Nobili's  rings  are 
known.  Prismatic  colors  which  make  their  ap- 
pearance when,  under  certain  circumstances,  an 
oxide  is  electrolyzed. 

Metallurgy. — The  art  of  working  metals  comprehend- 
ing the  whole  process  of  the  reduction  or  treat- 
ment of  metallic  ores  or  metals. 

Meteorites. — Fragments  of  solid  matter  in  space  which, 
when  coming  within  the  earth's  influence  are  at- 
tracted by  it,  becoming  incandescent  by  their 
passage  through  the  atmosphere. 

Meteorology. — The  science  which  treats  of  the  atmos- 
phere and  its  phenomena. 

Meter,  Electric. — An  instrument  employed  to  measure 
the  quantity  of  electricity  which  passes  in  a  speci- 
fied time  through  a  consumption  circuit. 

Meter-Motor. — A  small  motor  serving  to  operate  an 
electric  meter. 

Metre. — A  measure  of  length  equal  to  39,370  English 
inches  or  39,368  American  inches;  the  standard 
of  lineal  measure  intended  to  be  the  ten  millionth 


ELECTRICAL   DICTIONARY  155 

part  of  the  distance  from  the  equator  to  the  north 

pole. 
Metre-Bridge — A  slide  style    of   Wheatstone's  bridge, 

the  slide  wire  being  one  metre  long. 
Metric  Factors. — Factors  used  to  convert  the  units  of 

the  metric  system  into  those  of  other  systems. 
Metric  System  of  Weights  and  Measures. — A  system 

of  weights  and  measures  founded  on  the  gramme. 
Mica. — A  mineral  substance  more  or  less  transparent 

used  for  insulating  and  other  purposes. 
Micanite. — An  insulating  material  made  of  mica  and 

shellac. 

Micro. — A  prefix  meaning  the  one  millionth. 
Micro- Ampere. — The  millionth  of  an  ampere. 
Micro-Coulomb. — The  millionth  of  a  coulomb. 
Micro-Farad. — The  millionth  of  a  farad. 
Micrometer  Caliper. — A  Micrometer  gauge. 

Micrometer  Wire-Gauge. — A  delicate  form  of  wire 
gauge  fashioned  with  a  fine  thread  screw  and  a 
graduated  head  for  making  accurate  measure- 
ments of  wire  diameters. 

Microhm. — The  millionth  of  an  ohm. 

Microphone. — A  style  of  telephone  transmitter  used  on 

a  telephone  in  order  that  faint  sounds  may  be  made 

audible  and  clear. 

Microphone  Relay. — An  appliance  by  means  of  which 
a  telephonic  message  is  automatically  repeated 
over  another  wire. 

Microscope. — An  optical  instrument  for  examining  ob- 
jects which  are  too  minute  to  be  viewed  by  the 
naked  eye. 


156  ELECTRICAL  DICTIONARY 

Micro- Volt. — The  one  millionth  of  a  volt. 
Mil. — A  unit  of  length ;  one  thousandth  part  of  a  lineal 
inch. 

Mil-Foot. — A  unit  of  resistance  consisting  of  the  re- 
sistance of  a  foot  of  wire  one  thousandth  of  an 
inch  in  diameter.  The  resistive  standard  by  which 
wires  are  measured  or  compared. 

Milli. — A  prefix  meaning  the  one  thousandth  part. 

Milli-Ampere. — The  one  thousandth  of  an  ampere. 

Milli- Volt.— The  one  thousandth  of  a  volt. 

Mine  Explorer,  Electric. — A  small  magneto-electric 
generator  used  for  direct  blasting. 

Miniature  Incandescent  Lamp. — A  diminutive  incan- 
descent lamp  serviceable  for  dental,  surgical, 
microscopic  or  decorative  work. 

Mining  Locomotive,  Electric. — An  electric  locomotive 
used  in  mining  work. 

Minotto's  Voltaic  Cell. — A  cell  of  the  Daniell's  type 
having  at  the  bottom  of  the  ,cell  a  flat  copper  plate 
underneath  a  mass  of  copper  sulphate  crystals,  and 
filled  then  with  wet  sand  or  saw  dust,  upon  which 
the  zinc  plate  rests. 

Minus  Charge. — A  negative  charge. 

Mirror  Galvanometer. — A  galvanometer  the  deflections 
of  whose  needle  are  read  by  an  image  projected 
by  light  reflected  from  a  mirror  attached  to  the 
needle,  or  to  a  vertical  wire  carrying  the  needle. 

Mirror  Receiving-Instrument. — A  receiving  signaling 
instrument,  to  whose  needle  or  wire  carrying  it,  is 
attached  a  mirror,  and  which  is  used  in  sub-marine 
telegraphy. 


ELECTRICAL  DICTIONARY  157 

Mixed-Circuit  Board. — A  telephone  switchboard  con- 
nected with  mixed  circuits,  some  of  which  being 
metallic  and  the  others  ground  return  circuits. 

Mixed  Distribution. — A  distribution  of  electric  force 
combining  both  parallel  and  series  distribution. 

Moderate-Speed  Generator. — A  generator  constructed 
to  run  at  a  moderate  speed  and  in  that  respect 
differing  from  a  slow-speed  generator. 

Moderate-Speed  Motor. — A  motor  constructed  to  work 
at  a  moderate  speed  and  in  that  respect  differing 
from  a  slow-speed  motor. 

Molar  Attraction. — Gravitation.  The  attraction  of 
mass  for  mass  as  distinguished  from  molecular  at- 
traction. 

Molecular. — Pertaining  to  molecules. 

Molecular  Accommodation. — A  re-adjustment  of  the 
molecules  in  paramagnetic  material  which  results, 
by  continued  repetition,  in  a  diminution  in  the  hys- 
teretic  friction  in  cyclic  magnetization, 

Molecular  Agitation. — Quick  mechanical  vibration  im- 
parted to  a  mass  of  iron  in  order  to  diminish  its 
magnetic  hysteresis. 

Molecular  Attraction. — The  mutual  attraction  of  mole- 
cules for  each  other.  Physical  affinity.  Cohesion 
or  adhesion. 

Molecular  Bombardment. — The  collisions  occurring  be- 
tween contiguous  molecules  quickened  by  heat. 
The  movement  in  straight  lines  of  molecules  from 
the  negative  electrode  and  from  side  to  side  of  a 
vessel  when  the  residual  gas  therein  contained  is 
brought  to  a  sufficient  state  of  rarefaction ;  their 
courses  being  affected  by  heat  or  electric  discharge, 


158  ELECTRICAL  DICTIONARY 

which  causes  them  to  impinge  upon  the  positive 
electrode,  producing  luminous  effects. 

Molecular  Resistance. — The  resistance,  which  a  mass 
of  an  electrolyte  offers  when  contained  in  an  in- 
sulating vessel,  made  of  material  of  an  equal  spe- 
cific gravity  and  which  has  two  opposite  parallel 
conducting  faces,  at  a  distance  of  one  centimetre 
apart. 

Molecular   Vibration  of  Telephone  Diaphragm. — The 

molecular  vibration  which  takes  place  in  the  dia- 
phragm of  a  telephone  under  the  influence  of  modi- 
fications in  the  magnet's  magnetization;  marking 
a  distinction  as  to  its  molar  vibration. 

Molecule. — One  of  the  invisible  particles  supposed  to 
constitute  matter  of  any  kind.  The  minutest 
quantity  of  a  compound  substance  that  can  have 
existence. 

Moment. — The  product  of  the  force  by  the  shortest 
distance  from  the  point  of  rotation  to  the  exten- 
sion of  the  line  of  the  force,  when  a  force  is  applied 
so  as  to  tend  to  produce  rotation  around  a  point; 
such  distance  being  the  perpendicular  to  the  ex- 
tension of  the  line  through  the  point  of  rotation. 

Moment  of  a  Couple. — The  effective  power  of  a  couple. 
A  force  which  tends  to  cause  torsion  around  an 
axis,  as  in  the  pulling  or  turning  moment  of  the 
armature  of  an  electric  motor  upon  its  shaft. 

Moment  of  a  Magnet. — A  magnet's  polar  length  multi- 
plied by  the  intensity  of  magnetism  of  one  of  its 
poles. 

Momentary  Current. — A  current  which  flows  for  a 
short  time  only. 


ELECTRICAL  DICTIONARY  159 

Momentum. — The  quantity  of  motion  in  a  moving  body, 
being  always  proportioned  to  the  quantity  of  mat- 
ter multiplied  into  the  velocity.  Impetus. 

Mcnocyclic  Armature. — The  armature  of  a  monocycle 
generator  having  two  sets  of  windings,  one  con- 
stituting the  main  winding  and  corresponding  to 
that  of  an  ordinary  uniphaser,  the  other  being 
of  smaller  cross-section,  having  less  turns,  and  be- 
ing connected  in  diphase  relation,  to  the  center  of 
the  main  winding. 

Monocyclic  Generator. — A  style  of  polyphase  generator 
having  a  monocyclic  armature. 

Monocyclic  System. — An  alternating-current  distribu- 
tion system,  for  electric  lighting;  being  also  capa- 
ble of  operating  triphase  induction  motors.  A 
system  for  distributing  alternating  currents  using 
three  wires;  an  ordinary  uniphase  pressure  being 
maintained  between  two  of  them  while  there  is  a 
diphase  pressure  between  either  of  them  and  the 
third  one. 

Morse  Recorder. — An  apparatus  which  automatically 
records  the  dots  and  dashes  of  the  Morse  tele- 
graphic alphabet  on  a  ribbon  of  paper  drawn 
under  an  indenting  point  of  a  striking  lever  at- 
tached to  the  armature  of  an  electro-magnet ;  be- 
ing thus  distinguished  from  a  Morse  inker. 

Morse  System  of  Telegraphy. — A  telegraphic  system  in 
which  by  alternating  makes  and  breaks  of  varying 
duration  the  dots  and  dashes  of  the  Morse  alpha- 
bet are  reproduced  and  received  by  an  electro- 
magnetic sounder  or  other  receiver. 

Morse  Telegraphic  Sounder. — An  electro-magnet  which 


160  ELECTRICAL  DICTIONARY 

produces,  by  the  movement  of  its  armature  lever, 
the  dots  and  dashes  of  the  Morse  alphabet. 

Motor  Car,  Electric. — An  electrically  driven  car. 

Motor  Circuit. — A  circuit  supplying  an  electric  motor 
or  motors. 

Motor-Controlling  Rheostat. — A  rheostat  which  is  con- 
nected with  a  motor  and  serves  to  start  the  motor 
or  govern  its  speed. 

Motor  Cut-Out. — A  cut-out  in  the  circuit  of  a  motor 
provided  for  the  purpose  of  throwing  it  out  of 
circuit. 

Motor-Dynamo. — A  motor  electrically  driven  and  firmly 
connected  to  the  armature  of  a  dynamo  for  the 
purpose  of  modifying  the  current. 

Motor  Starting-Box. — A  box  equipped  with  a  starting 
rheostat  or  controller. 

Motor  Starting-Rheostat. — An  adjustable  rheostat  de- 
signed to  prevent  an  abnormal  flow  of  current 
through  a  shunt-wound  motor  when  starting. 

Motor  Torque. — The  rotary  effort  which  an  electric 
motor  develops. 

Motor-Transformer. — A  transformer  which  a  motor 
operates.  A  motor-generator,  rotary  transformer 
or  dynamotor.  A  dynamo-electric  machine  pro- 
vided with  two  armature  windings ;  one  serving  to 
receive  current  as  a  motor,  the  other  to  deliver 
current,  as  a  generator,  to  a  secondary  circuit. 

Motor  Truck. — The  truck  of  an  electric  car  equipped 
with  supports  from  which  to  suspend  an  electric 
motor. 

Moulded  Carbons. — Carbons  artificially  manufactured 


ELECTRICAL   DICTIONARY  161 

by  subjecting  carbonaceous  substances  to  pressure 
in  a  mould. 

Moulded  Mica. — A  substance  used  for  insulating  and 
made  of  finely  broken  mica  formed  into  a  paste 
with  insulating  material  and  moulded,  before  cool- 
ing, into  the  shape  required. 

Moulding  Wiring. — Wiring  effected  by  enclosing  the 
wires  in  suitably  shaped  moulding  which  is  placed 
on  the  walls  or  ceiling  of  a  room. 

Mouldings  Electric. — Mouldings  made  of  seasoned  non- 
conducting wood,  longitudinally  grooved,  in  order 
to  receive  and  hold  insulated  wires. 

Mouth-Pieces. — Circular  orifices  communicating  with 
the  air  chambers  placed  over  the  diaphragms  of 
telephones,  graphophones,  gramophones  or  phono- 
graphs to  facilitate  the  application  of  the  mouth 
when  speaking,  in  order  to  produce  vibration  in 
the  diaphragm. 

Movable  Secondary. — The  secondary  of  an  induction 
coil  which  is  movable  instead  of  being  rigid  as  in 
most  coils. 

Multi-Circuit  Arc-Dynamo. — A  dynamo  with  an  arma- 
ture which  has  several  circuits  and  intended  to 
avoid  too  great  an  electro-motive  force  on  any  one 
circuit. 

Multi-Circuit  Arc-Light  Generator. — An  arc-light  gene- 
rator intended  to  furnish  current  to  a  number  of 
series-connected  arc-circuits,  being  in  this  respect 
distinguished  from  one  intended  to  supply  one  cir- 
cuit only. 

Multiphase. — Containing  more  than  one  phase. 

Multiphase  Alternating-Currents. — Several  separate  al- 


162  ELECTRICAL  DICTIONARY 

ternating  currents  which  vary  in  phase  by  an 
established  amount. 

Multiphase  Alternator. — An  alternator  having  the  ca- 
pacity to  produce  multiphase  currents. 

Multiphase  Apparatus. — A  term  applied  generally  to 
multiphase  motors,  alternators,  or  other  receptive 
apparatus  serviceable  on  multiphase  circuits. 

Multiphase  Induction-Motor. — An  induction  motor  ope- 
rated by  rotating  magnetic  fields  and  serviceable 
in  connection  with  multiphase  currents. 

Multiphase  Synchronous-Motor. — A  synchronous  alter- 
nating-current motor  furnished  with  multiphase 
currents,  as  contrasted  with  an  asynchronous  or 
induction  multiphase  motor. 

Multiphaser. — A  multiphase  alternator. 

Multiple- Arc -Circuit. — A  term  frequently  applied  to  a 
multiple  circuit. 

Multiple-Arc  Connected  Sources. — A  battery  consisting 
of  multiple  connected  sources. 

Multiple  Armature- Windings. — A  term  applied  at  times 
to  multiple-circuit  armature  windings. 

Multiple  Cable. — A  cable  having  more  than  one  con- 
ducting wire  or  circuit. 

Multiple  Circuit. — A  circuit  in  which  the  positive  poles 
of  a  number  of  separate  sources  and  receptive  de- 
vices are  connected  to  a  single  positive  lead  or 
conductor;  their  negative  poles  being  connected  to 
a  single  negative  lead  or  conductor. 

Multiple-Circuit  Multiple-Wound  Armature. — An  ar- 
mature providing  a  number  of  circuits  between  the 
brushes,  and  in  addition,  a  number  of  independent 


ELECTRICAL  DICTIONARY  163 

windings  which  are  connected  to  independent  com- 
mutator bars  symmetrically  interspersed. 

Multiple-Pair  Brush- Yoke. — A  contrivance  which  holds 
a  number  of  pairs  of  brushes  on  the  commutator 
in  a  manner  enabling  them  all  to  be  simultaneously 
moved  or  rotated  on  it. 

Multiple-Parallel  Circuit. — A  term  at  times  applied  to 
a  multiple  of  parallel  circuits. 

Multiple  Rheostat. — A  rheostat  the  resistances  of  which 
can  be  thrown  into  a  circuit  in  multiple,  thereby 
increasing  the  carrying  capacity  as  the  resistance 
decreases. 

Multiple  Running. — The  running  of  generators  in  paral- 
lel. 

Multiple-Series. — Series  groups  connected  in  multiple. 

Multiple-Series  Circuit. — A  circuit  wherein  a  number 
of  individual  sources  or  receptive  devices  or  both 
are  connected  in  series  in  a  number  of  separate 
groups,  these  groups  being  subsequently  connected 
in  multiple. 

Multiple-Series-Connected  Sources. — A  number  of  in- 
dividual electric  sources  connected  in  multiple- 
series  in  such  manner  as  to  be  able  to  act  as  single 
sources. 

Multiple  Unit  System  of  Railway  Traction. — A  system 
of  electric  railroad  wherein  each  traction  unit  is 
supplied  with  its  own  independent  motors,  so  that 
all  the  units  may  be  operated  from  a  single  point 
collectively. 

Multiple  Windings. — Independent  windings  arranged 
in  a  symmetrical  manner  upon  the  same  armature 
and  insulated  from  each  other,  yet  carried  to  dif- 
ferent segments  of  the  commutator. 


164  ELECTRICAL  DICTIONARY 

Multiple- Wound  Multiple-Circuit  Armature. — A  multi- 
polar  armature  provided  with  a  number  of  wind- 
ings each  winding  having  a  number  of  circuits 
between  the  brushes. 

Multiple-Wound  Two-Circuit  Armature- Windings  .—A 

multipolar  armature  with  a  number  of  windings, 
there  being  two  circuits  between  the  brushes  for 
each  winding. 

Multiple  Working  of  Dynamo^Electric  Machines. — A 

term  used  sometimes  to  signify  the  parallel  work- 
ing of  dynamo  electric  machines. 

Multiplex  Telegraphy. — A  system  of  telegraphy  which 
provides  for  the  simultaneous  transmission  of  more 
than  two  separate  messages  in  opposite  directions 
and  over  a  single  wire  from  each  end. 

Multipolar  Armature. — An  armature  employed  in  a 
multipolar  field. 

Multipolar-Drum  Armature- Windings. — Windings  of  a 
drum  armature  adaptable  to  a  multipolar  field. 

Multipolar  Dynamo. — A  dynamo  having  a  multipolar 
field. 

Multipolar  Field. — A  field  generated  by  several  sepa- 
rate magnets. 

Multipolar  Generator. — A  multipolar  dynamo. 

Multipolar  Motor. — A  motor  the  field  magnets  of  which 
have  several  separate  magnet  poles. 

Multipolar  Railway-Generator. — A  generator  provided 
with  a  multipolar  field  and  serving  to  supply  cur- 
rent to  trolley  cars. 

Multipolar-Ring  Armature- Winding. — A  winding  of  a 
ring  armature  suitable  for  a  multipolar  field. 


ELECTRICAL   DICTIONARY  165 

Municipal  Series  Circuit. — A  series  circuit  serving  to 
distribute  lights  and  adaptable  for  lighting  streets. 

Municipal  System  of  Incandescent  Electric  Lighting.— 
A  system  of  distribution  for  incandescent  electric 
lighting  wherein  the  individual  lamps  are  con- 
nected to  the  circuit  in  series,  each  lamp  being 
equipped  with  an  automatic  cut-out. 

Mutual  Flux  of  Transformer. — The  magnetic  flux 
which  flows  through  both  of  a  transformer's  coils 
as  contrasted  with  magnetic  flux  which  may,  when 
excited,  pass  through  one  coil  to  the  exclusion  of 
the  other. 

Mutual  Induction — Induction  which  two  adjacent  cir- 
cuits produce  on  each  other  by  the  mutual  inter- 
connection of  their  magnetic  fluxes.  Induction 
caused  in  charged  conductors  adjacent  to  each 
other,  by  the  inter-connection  of  their  electrostatic 
fluxes. 

Myograph. — An  instrument  employed  to  determine 
nervous  sensibility. 

Myopia. — Near-sightedness. 

Myria. — A  prefix  meaning  ten  thousand  times. 


N. 

N. — An  abbreviation  for  North-seeking  magnet. 

N.  H.  P. — An  abbreviation  for  nominal  horse  power. 

Name  Plate. — A  plate  attached  to  a  dynamo-electric 
machine  giving  the  maker's  name  and  such  other 
information  as  weight,  power,  speed,  current,  etc. 

Natural  Law. — The  co-relation  of  phenomena.    The  in- 


166  ELECTRICAL  DICTIONARY 

variable  sequence  attending  the  manifestation  of 
phenomena. 

Natural  Magnet. — See  Lodestone. 

Nautical  Mile. — A  knot.  A  distance  equal  to  6,087  feet 
or  about  1.15  statute  miles,  and  the  one-twenty- 
one  thousand  six-hundredth  of  the  circumference 
of  the  earth  at  the  equator  or  one-sixtieth  of  a  de- 
gree of  longitude  at  the  equator. 

Nautical  Telegraphy. — Telegraphic  communication  at 
sea  between  vessels  and  aboard  single  vessels. 

Needle. — A  word  meaning  a  magnetic  needle. 

Needle  Annunciator. — An  annunciator  which  indicates 
with  a  needle  instead  of  by  the  fall  of  a  drop. 

Needle  System  of  Telegraphy. — A  system  of  telegraphy 
which  provides  for  the  indication  of  the  letters  in 
the  alphabet  and  numerals  by  the  oscillating  move- 
ment of  a  magnetic  needle. 

Needle  Telegraph. — A  term  in  general  use  signifying 
the  apparatus  used  in  needle  telegraphy. 

Negative  Brush  of  Motor. — The  brush  which  is  con- 
nected with  the  negative  terminal  of  a  dynamo.  - 

Negative  Electricity. — A  phase  of  electric  excitement, 
observable,  for  instance,  when  resin  is  rubbed  with 
silk. 

Negative  Electrode. — The  electrode  which  is  connected 
to  a  source's  negative  terminal. 

Negative  Feeder. — Feeders  which  connect  the  negative 
mains  with  the  negative  poles  of  a  generator. 

Negative  Plate  of  Storage  Cell. — The  plate  of  a  storage 
cell  which,  by  the  action  of  a  current,  becomes 
partly  covered  with  a  coating  of  spongy  lead.  The 
plate  of  a  storage  cell  which  is  connected  to  a 


ELECTRICAL  DICTIONARY  167 

charging  source's  negative  terminal,  constituting 
therefore  the  negative  pole  of  the  cell  on  discharg- 
ing. 

Negative  Plate  of  Voltaic  Cell.— The  electro-negative 
element  of  a  voltaic  couple.  That  part  of  a  voltaic 
cell's  plate  above  the  liquid  which  becomes  the 
positive  pole  of  the  cell. 

Negative  Pole  of  Source. — The  pole  of  an  electric  source 
through  which  the  current  is  supposed  to  go  in 
or  to  pass  back  into  the  source,  after  having  passed 
through  the  circuit  connected  to  the  source. 

Negative  Side  of  Circuit. — That  side  of  a  circuit  which 
is  opposite  the  positive  sides.  The  side  of  a  circuit 
into  which  current  flows  after  having  performed 
a  duty  or  function.  That  side  of  a  circuit  which 
is  connected  with  the  negative  pole  of  a  source. 

Net  Efficiency. — The  ultimate  efficiency  of  machines  or 
transferring  contrivances  through  which  energy 
must  pass  in  distinction  from  the  separate  effic- 
iency of  each  machine  or  device. 

Network  of  Conductors. — A  term  used  to  describe  a 
number  of  conductors  so  interconnected  as  to  re- 
semble a  net  in  appearance. 

Neutral  Ampere-Meter. — An  ampere  meter  in  a  three- 
wire  system  of  distribution  which  is  connected 
with  the  neutral  bus-bar. 

Neutral  Conductor. — In  a  three-wire  system,  the  neu- 
tral wire. 

Neutral  Feeder. — The  feeder  connected  with  the  neu- 
tral bus-bar  in  a  three-wire  system. 

Neutral-Line  of  Magnet. — The  equator  of  the  magnet. 

Neutral  Point. — A  term  signifying  indifference. 


168  ELECTRICAL  DICTIONARY 

Neutral  Points  of  Magnet. — Points  which  are  nearly 
midway  between  the  poles  of  a  magnet. 

Neutral  Salt. — A  salt  devoid  of  basic  o-r  acid  properties. 

Neutral  Wire. — The  wire,  in  a  three-wire  system  of 
distribution,  which  is  connected  with  the  neutral 
dynamo  terminals.  Of  a  three-wire  system,  the 
balance  wire. 

Nickel  Bath. — An  electrolytic  bath  which  contains  a 
salt  of  nickel  easily  electrolyzable,  having  a  nickel 
plate  which  serves  as  the  anode  of  the  battery,  and 
which  is  immersed  in  a  liquid  in  proximity  to  the 
article  to  be  plated,  which  serves  as  the  cathode. 

Nipple  of  Negative  Carbon. — A  diminutive  elongation 
of  the  carbon  which  occurs  on  the  surface  of  the 
negative  carbon  facing  the  crater  of  the  positive 
one  while  the  arc  is  going. 

Noise. — A  confused  collection  of  discordant  tones. 
Clamor.  Din. 

Noisy  Arc. — A  voltaic  arc  which  emits  frying  and  hiss- 
ing sounds  during  maintenance. 

Nominal  Candle-Power . — A  term  used  at  times  signify- 
ing the  candle-power  of  a  luminous  source  obtained 
in  a  suitable  direction. 

Non-Arcing  Fuse. — A  fuse  wire  which,  by  reason  of 
being  made  of  non-arcing  metal,  or  encased  in  an 
air-tight  tube,  blows  without  forming  a  voltaic  arc. 

Non-Arcing  Metal. — An  alloy  composed  of  the  blend- 
ing of  a  certain  assemblage  of  metals,  which  will 
not,  under  some  conditions  allow  an  alternating- 
current  arc  to  be  maintained  between  them. 

Non-Conductor. — A  material  of  low  conductivity  or 
high  electric  resistance. 


ELECTRICAL  DICTIONARY  169 

Non-Ferric. — Without  iron. 

Nan-Ferric  Inductance. — An  inductance  of  a  circuit  de- 
void of  iron  or  not  associated  magnetically  there- 
with. The  inductance  possessed  by  a  coil  which 
has  a  non-magnetic  core. 

Non-Ferric  Magnetic  Circuit. — A  magnetic  circuit  with- 
out iron,  or  one  which  contains  only  non-magnetic 
materials,  such  as  copper,  wood,  air,  etc. 

Non-Homogeneous  Current-Distribution. — That  distri- 
bution of  current  which  flows  through  a  conduc- 
tor, wherein  there  is  over  any  cross-section  of  it, 
a  current  of  unequal  density. 

Non-Magnetic  Steel. — Alloys  of  irons  incapable  of  be- 
ing magnetized,  composed  of  such  substances  as 
manganese  or  nickel  steel. 

Non-Oscillatory. — Not  changing  the  direction  of  mo- 
tion ;  not  oscillating  in  motion. 

Non-Polar  Transformer. — A  term  applied  to  a  closed 
iron-circuit  transformer. 

Non-Polarizable. — Devoid  of  the  ability  of  being  polar- 
ized. 

Non-Polarized  Armature. — An  armature  composed  of 
soft  iron  and  which,  regardless  of  the  direction 
in  which  the  current  flows  through  the  coils,  is 
drawn  towards  the  poles  of  an  electro-magnet, 
when  the  circuit  is  completed. 

Non-Synchronous  Motor.  —  An  alternating  current 
motor  possessing  the  ability  to  start  at  any  load; 
one  not  forced  to  run  in  concurrence  with  its  driv- 
ing current. 

Normal. — Consonant  with  rule.    Regular. 


X70  ELECTRICAL,  DICTIONARY 

Normal  Current. — The  force  of  current  at  which  a  sys- 
tem is  intended  to  work. 

Normal  Voltage. — The  voltage  at  which  a  system  is  in- 
tended to  work. 

North-Seeking  Magnetic  Pole. — The  pole  of  a  magnet 
which  points  to  the  earth's  north  geographical 
pole. 

Nose  Suspension  of  Motor. — The  hanging  of  a  motor 
in  a  car  truck  by  a  hook  from  above  instead  of 
from  a  bar  and  spring  from  underneath. 

Null  of  Zero  Method. — Any  method  by  which  compari- 
sons or  measurements  are  secured,  the  accuracy  of 
the  measurements  being  determined  by  the  de- 
flection of  the  galvanometer  being  null  or  nought. 
For  example,  the  Wheatstone  bridge. 


0. 

0. — An  abbreviation  for  ohm. 

0.  K. — A  telegraphic  signal  meaning  "yes"  or  "all 
right." 

Obtuse  Angle. — A  term  applied  to  an  angle  greater 
than  a  right  angle  or  containing  more  than  90 
degrees. 

Occluded-Gas  Process. — A  method  of  depleting  a 
vacuum  tube  or  incandescent  electric  lamp  cham- 
bers of  the  residual  air,  and  which  is  effected  by 
the  application  of  a  high  degree  of  temperature 
to  the  tube  or  lamp  before  sealing,  and  while  con- 
nected with  the  pumps. 

Octo-Polar  Dynamo. — A  multipolar  dynamo  the  field 
of  which  possesses  eight  poles. 


ELECTRICAL  DICTIONARY  171 

Octo-Polar  Field. — A  field  resulting  from  the  flux  of 
eight  distinct  magnetic  poles. 

Off  Position  of  Switch. — The  position  assumed  by  a 
switch  when  throwing  off,  from  the  working  cur- 
rent, a  section  of  a  circuit, 

Ohm. — The  practical  unit  of  resistance;  electro-mag- 
netic units  109  degrees  C.  G.  S.  A  resistance  such 
as  would  confine  the  electric  flow  under  an  electro- 
motive force  of  one  volt  to  a  current  of  one  ampere 
or  coulomb  per  second. 

Ohmage. — The  value  of  a  circuit's  resistance  expressed 
in  ohms. 

Ohmic. — Pertaining  to  the  ohm. 

Ohmic  Drop. — The  drop  in  pressure  resulting  from 
ohmic  pressure. 

Ohmic  Resistance. — A  resistance  in  distinction  from 
spurious  resistance,  or  counter-electro-motive  force. 

Ohm  Meter. — An  instrument  serving  to  measure  di- 
rectly the  resistance  of  a  conductor  or  of  any  sec- 
tion of  a  circuit  through  which  a  strong  current 
is  flowing. 

Ohm  Mile. — A  standard  of  conductivity  consisting  of 
wires  one  mile  long  and  which  offer  a  resistance  of 
one  ohm  at  a  standard  temperature.  A  mass  of 
material,  which  would  at  a  standard  temperature 
enable  a  wire  of  that  material  to  show  a  resistance 
of  one  ohm. 

Ohm's  Law. — The  basic  law  which  expresses  the  rela- 
tions between  current  electro-motive  force  and  re- 
sistance in  active  electric  circuits. 

Oil  Insulator. — An  insulator  containing  oil. 


172  ELECTRICAL   DICTIONARY 

Oil  Paper. — A  material  for  insulating  composed  of 
paper  which  has  been  saturated  with  an  insulating 
oil. 

Oil  Transformer. — A  transformer  put  into  oil  for  the 
purpose  of  securing  and  maintaining  high  insula- 
tion. 

Okonite. — A  kind  of  insulating  material. 

One-Layer  Armature- Winding. — An  armature  winding 
which  consists  of  one  layer  of  wire  only. 

Opacity. — Not  possessing  the  property  of  transparency. 

Open-Arc. — A  voltaic  arc  not  enclosed. 

Open  Car- Wheel. — A  style  of  car-wheel  containing  per- 
forations in  the  space  between  the  flange  and  the 
journal. 

Open  Circuit. — A  circuit  which  is  broken. 

Open-Circuit  Battery. — A  battery  employed  in  open- 
circuit  work,  its  principal  requirement  being  that 
it  must  not  run  down  or  become  exhausted  when 
left  on  open  circuit. 

Open-Circuit  of  Triphase  Connections. — The  triphase 
circuit's  star-connection. 

Open-Circuit  Thermostat. — A  thermostat  employed  on 
an  open-circuit. 

Open-Circuit  Transformer. — A  transformer  the  mag- 
netic circuit  of  which  is  completed  to  some  extent 
through  air. 

Open-Circuited. — Having  an  open  or  broken  circuit. 

Open-Coil  Armature. — An  armature  which  has  some  of 
its  coils  on  open  circuit  during  a  part  of  the  ar- 
mature's rotation. 

Open-Coil  Drum  Dynamo-Electric  Machine. — An  open- 


ELECTRICAL  DICTIONARY  173 

coil  dynamo-electric  machine  with  a  drum-wound 
armature. 

Open- Wire  Symmetrical  Twist. — A  method  of  running 
aerial  telephone  wires  with  a  view  to  obviating 
cross-talk;  all  the  wires  on  a  pole  being  twisted 
along  the  line. 

Open  Work. — Open  wiring. 

Opening  a  Circuit. — The  breaking  of  a  circuit. 

Opening  Shock. — The   shock  resulting  in  an  electric 

circuit  containing  self-induction  upon  opening  or 

breaking  the  same. 
Operator's  Set. — A  telephone  set  used  by  the  operator 

at  a  central  station. 
Optics. — The  science  which  treats  of  the  phenomena  of 

light. 
Optical  Efficiency  of  Light. — The  relation  between  the 

obscure  and  luminous  radiation. 

Optical  Strain. — A  defect  in  a  plate  of  any  transparent 
medium  produced  by  the  action  of  a  stress  and 
accompanied  by  a  modification  in  the  optical  prop- 
erties of  the  medium. 

Ordinate. — The  distance  of  any  point  from  the  axis  of 
abscissas,  in  a  system  of  plane  co-ordinates,  meas- 
ured parallel  to  the  axis  of  ordinates. 

Ordinary  Relay. — A  relay  not  polarized. 

Oscillating  Current. — A  current  periodically  alternat- 
ing. 

Oscillation. — A  vibration  or  movement  back  and  forth. 

Oscillations,  Electric. — The  rapid  and  sudden  alterna- 
tions, in  static  electricity,  attending  the  discharge 
of  a  static  condenser ;  the  discharge  being  of  a  dis- 


174  ELECTRICAL  DICTIONARY 

ruptive  character,  but  appearing  to  consist  of  a 
number  of  discharges  which  alternate  in  direction 
and  produce  electro-magnetic  ether  waves  of  the 
same  nature  as  light  waves;  the  latter,  however, 
being  shorter  and  much  less  rapid. 

Oscillator. — A  device  which  produces  oscillations. 

Oscillator,  Electric. — A  device  serving  to  produce 
electric  currents  of  a  steady  period  without  regard 
to  any  variations  in  its  driving  force. 

Oscillatory  Dynamo. — A  dynamo  which  has  electro- 
motive forces  generated  in  its  armature  coils  by  a 
vibratory  or  oscillatory  movement  through  a  mag- 
netic field. 

Osmose. — The  equal  blending  of  liquids  with  varying 
densities  through  the  pores  of  a  separating 
medium. 

Osmose,  Electric. — When  two  liquids  are  separated  by 
a  porous  diaphragm  and  a  strong  current  of  elec- 
tricity is  passed  through  from  the  liquid  on  the 
one  side  .through  the  diaphragm,  to  the  liquid  on 
the  other  side,  the  liquid  on  the  side  to  which  the 
current  is  passing  rises  in  level. 

Outboard  Bearing. — A  journal  bearing  extended  be- 
yond the  base  frame  of  a  machine  in  order  to  ob- 
tain sufficient  support  for  a  long  or  heavy  shaft. 

Outboard   Bearing   of  Dynamo-Electric   Machine. — A 

bearing  extended  beyond  the  base  frame  of  a 
dynamo  electric  machine  in  order  to  properly  sup- 
port the  motor. 

"Out-door"  Transformer. — A  transformer  located  out- 
side of  a  building  at  a  suitable  place. 


ELECTRICAL  DICTIONARY  175 

Outgoing  Current. — The  current  which  goes  out  from 
a  station  over  a  line. 

Outlet. — A  point  in  a  wall  or  ceiling  where  branch 
wires  come  out  and  which  are  to  be  connected  to 
a  switch,  lamp,  etc.  The  places  about  a  building 
where  the  fixtures  or  lamps  are  attached. 

Outlet  Block. — A  fuse  block  located  at  or  close  to  an 
outlet.  A  block  which  has  an  outlet  protected  by 
a  fuse  wire. 

Outlet  Box. — A  box  located  at  or  close  to  an  outlet  to 
facilitate  the  making  or  changing  of  electric  con- 
nection with  the  outlet  conductors. 

Output. — The  useful  energy  which  any  machine  gives 
out. 

Output  of  Dynamo-Electric  Machine. — The  electric 
power  of  current  which  a  dynamo  electric  gene- 
rator develops  at  the  delivery  terminals  and  in- 
dicated in  volt-amperes,  kilo-watts  or  watts. 

Outrigger. — An  arm  attached  at  right  angles  to  a  pole 
in  order  to  support  it. 

Outrigger  for  Arc-Lamp. — A  fixture  attached  at  right 
angle  to  the  vault  of  a  building  for  the  purpose 
of  suspending  an  electric  arc-lamp  therefrom. 

Outside  Wiring. — The  wiring  outside  of  a  building  or 
structure  for  a  circuit. 

Over-Compounded. — Compound  winding  of  such  a 
character  on  a  dynamo-electric  machine  that  the 
voltage  at  its  terminals  is  caused  to  increase  under 
a  greater  load. 

Over-Compounded  Dynamo. — A  dynamo,  the  magneto- 
motive force  of  whose  series  coils  compensates  for 
the  drop  in  the  armature  and  for  the  drop  in  a 


176  ELECTRICAL   DICTIONARY 

conductor  ranging  from  the  generators  to  the 
motors,  thus  allowing  the  outer  conductors  to  be 
considered  as  an  extension  of  the  armature  wind- 
ing, whereby  the  generator  delivers  a  constant 
pressure  at  its  terminals  at  the  motor. 

Overhead  Conductor. — A  conductor  erected  overhead. 

Overhead  Feeders. — Feeders  erected  overhead. 

Overhead  Switch. — A  switch  placed  overhead  and  serv- 
ing to  control  an  overhead  circuit,  also  one  placed 
on  a  car  over  the  motorman  for  his  ready  manipu- 
lation. 

Overhead  Trolley-System. — A  system  in  which  the  cur- 
rent that  propels  an  electric  street  car  is  taken 
from  a  wire  overhead. 

Overhead  Trolley- Wire. — A  common  aerial  trolley  wire. 

Overlapping    Winding    of    Alternator    Armature. — A 

winding  by  overlapping  the  successive  coils  in 
contrast  to  one  by  mechanically  separating  suc- 
cessive coils. 

Overload. — A  load  having  an  abnormal  value.  Too 
heavy  a  load. 

Overload  of  Electric  Motor. — A  load  in  excess  of  that 
which  an  electric  motor  is  designed  to  carry  with 
its  greatest  operating  efficiency.  A  load  so  ex- 
cessive as  to  produce  damage  to  the  motor  by  heat- 
ing. 

Overload  Switch. — A  switch  provided  in  order  to  open 
a  circuit  automatically  in  case  of  an  overload. 

Overloaded  Conductor. — A  conductor  loaded  with  an 
electric  current  greater  than  that  for  which  it  was 
designed. 


ELECTRICAL  DICTIONARY  177 

Over- Winding  of  Series  Motor. — A  series  motor  having 

too  strong  a  field  winding. 
Over- Wound  Motor  Field. — A  motor  field  in  which  the 

full  strength  is  developed  with  much  less  current 

than     usually     required.       An     over-compounded 

motor  field.  • 
Ozone. — Oxygen  in  an  active  or  highly  electro-negative 

state. 
Ozonizer. — An  apparatus  employing  electric  discharges 

to  produce  ozone. 


P. 

Pacinotti  Projections. — Teeth  in  an  armature  core 
projecting  radially  from  the  central  shaft  in  a 
manner  to  form  slots  or  chambers  for  the  insertion 
of  the  armature  coils. 

Pacinotti  Ring. — An  armature  core  in  the  form  of  a 
ring  with  projections  and  serving  for  the  recep- 
tion of  the  armature  winding  in  Pacinotti 's  gene- 
rator. 

Packing  of  Telephone  Dust  Transmitter. — The  forming 
into  a  cake  of  carbon  dust  in  a  transmitter  which 
materially  impairs  the  efficiency  of  the  apparatus. 

Palladium. — A  metal  of  the  platinum  group. 

Palladium  Alloys. — Divers  alloys  composed  of  pal- 
ladium with  metals  principally  having  no  para- 
magnetic properties  and  used  where  desirable  to 
obtain  freedom  from  the  disturbance  of  powerful 
magnetic  fields,  as,  for  instance,  the  hairsprings 
of  watches. 


178  ELECTRICAL  DICTIONARY 

Panel  Board. — A  switchboard  built  and  connected  in 

panels. 

Panel  of  Switchboard. — A  sub-section  of  a  panel  board. 
Paper  Cable. — A  cable  insulated  with  paper. 
Paper    Carbon. — Filaments    for    incandescent    lamps. 

made  of  carbonized  paper. 
Paper  Insulation. — Insulation  made  of  paper. 
Parabola. — A  curve  known  as  one  of  the  conic  sections 

and  formed  by  the  intersection  of  the  surface  of  a 

cone  with  a  plane  parallel  to  one  of  its  sides. 

Parabolic  Reflector. — A  reflector  of  light  or  a  mirror 
whose  surface  is  a  paraboloid  and  which  reflects 
in  lines  parallel  with  each  other  the  rays  of  a  light 
located  at  its  focus. 

Paradox. — Something  seemingly  absurd  or  contradic- 
tory ;  but  yet  true  in  fact. 

Paraffine. — A  hydro-carbon  very  valuable  for  insulat- 
ing. The  wax  from  mineral  oils. 

Paraffined  Wire. — Wire  whose  textile  covering  is 
coated  with  paraffine. 

Paraffining. — Coating  with  paraffine. 

Parallel  Circuit. — A  term  signifying  multiple  circuit. 

Parallel  Connected  Triphasers. — Several  triphasers 
which  are  connected  parallel  with  an  ordinary  set 
of  triphase  mains. 

Parallel  Coupling. — A  term  applied  at  times  to  the  par- 
allel connection  of  generators. 

Parallel  Distribution. — A  distribution  of  electricity 
wherein  the  receptive  contrivances  are  adjusted 
between  two  or  every  two  of  a  number  of  parallel 
conductors  running  to  the  limits  of  the  system. 


ELECTRICAL  DICTIONARY  179 

Parallel  Feeding. — Supplying  the  necessary  current  to 
a  number  of  receptive  contrivances  connected  in 
parallel. 

Parallel  Series. — A  term  used  signifying  a  multiple- 
series  connection. 

Parallel  Transformer. — A  transformer  employed  in  a 
parallel  system  of  distribution  or  connected  with 
parallel  mains. 

Parallel- Working  of  Dynamo-Electric  Machines. — Sev- 
eral dynamos  operating  parallel. 

Paramagnet. — A  magnet  obtained  from  the  magnetic 
influence  of  iron  or  other  magnetic  substance. 

Paramagnetic. — Having  magnetic  properties  or  the 
capacity  to  concentrate  magnetic  lines  of  force. 

Paramagnetic  Permeability. — Susceptible  to  penetra- 
tion by  magnetic  force. 

Partial  Contact. — Defective  contact  producing  high 
resistance  in  two  telegraphic  circuits. 

Partial  Disconnection. — A  defective  metallic  contact, 
or  lack  of  perfect  metallic  connection. 

Partial  Vacuum. — A  vacuum  not  complete. 

Party  Lines  for  Telephone  Service. — Lines  by  which  a 
number  of  subscribers  in  one  circuit  are  connected, 
as  distinguished  from  lines  assigned  to  single  sub- 
scribers. Or,  lines  by  which  a  number  of  tele- 
phonic stations  are  connected  together  in  contrast 
to  those  which  connect  each  station  through  an  ex- 
change. 

Parz  Gravity  Cell. — A  couple  consisting  of  zinc-carbon 
used  with  common  salt  or  sulphate  of  magnesia 
and  sulpho-chromis  salt,  the  different  density  of 
the  liquids  keeping  them  separated  in  the  cell. 


180  ELECTRICAL  DICTIONARY 

Paste  Joint  for  Lamp  Filament. — A  species  of  joint 
made  of  a  moist  hydro-carbon  paste  and  then  car- 
bonized, and  used  between  leading-in  wires  and 
the  ends  of  a  lamp  filament. 

Pasted  Secondary  Cell. — A  secondary  cell  where  a 
paste  or  cement  composed  of  the  active  material 
is  applied  to  the  surface  of  the  grid. 

Path  of  Magnetic  Leakage. — A  path  followed  by  es- 
caping magnetic  flux  from  the  main  path  where  it 
is  usefully  employed. 

Patrol  Alarm-Box. — A  box  designed  for  the  use  of  a 
patrol  in  telegraphic  or  telephonic  systems  where- 
by any  call  or  alarm  can  be  given. 

Paying-Out. — Passing  out  submarine  cable  while  it  is 
being  laid  from  a  ship. 

"Pea"  Lamp. — A  very  diminutive  form  of  incandes- 
cent lamp. 

Pear  Push. — A  push  contact  resembling  a  pear  in  shape 
and  attached  to  the  end  of  a  pendant  flexible  cord. 

Peltier  Effect. — The  heating  effect  produced  by  the 
passing  of  a  current  through  the  junction  of  two 
unlike  conductors. 

Pencil  Microphone. — A  carbon  microphone,  the  loose 
carbon  being  in  the  form  of  a  pencil  or  pencils. 

Pendant  Cord. — A  flexible  conductor  by  means  of 
which  a  pendant  lamp  or  push  is  supplied  with 
current. 

Pendant,  Electric. — A  suspended  fixture  upon  which 
an  incandescent  lamp  or  contact  is  supported  and 
held  in  a  socket  attached  to  it. 

Pendulum,  Electric. — A  pendulum  which  the  inter- 
mittent action  of  an  electro-magnet  actuates,  the 


ELECTRICAL  DICTIONARY  181 

pendulum  itself  opening  and  closing  the  circuit  by 
means  of  a  point  at  its  lower  extremity  contacting 
as  it  swings  to  and  fro  through  a  globule  of  mer- 
cury, thus  opening  and  closing  the  circuit. 

Penthode  Working. — A  five-way  method  of  telegraphic 
working  which  is  obtained  by  the  employment  of 
the  synchronous  multiplex  system  of  Delaney. 

Percentage  Conductivity. — The  percentage  of  conduc- 
tivity of  a  conductor  based  upon  the  Mathiessen 
standard. 

Percentage  Conductivity  of  Wire. — The  conductivity 
of  wire,  taking  as  a  standard  the  conductivity  of 
pure  copper.  The  conductivity  of  wire  based  upon 
the  Mathiessen  standard  of  conductivity  for 
copper. 

Perforated  Armature. — An  armature  having  perfora- 
tions for  the  introduction  of  the  coils. 

Period. — The  time  necessary  to  effect  the  completion 
of  a  periodic  motion.  The  full  alternation  of  an 
oscillatory  discharge  or  of  an  alternating  current. 

Period  of  Vibration. — The  time  consumed  by  the  ex- 
ecution of  a  complete  vibration  or  movement  back 
and  forth. 

Periodic. — Pertaining  to  a  period. 

Periodic  Alternating  Electromotive  Force. — An  electro- 
motive force  with  periodically  varying  direction. 

Periodic  Current. — A  current  with  periodically  varying 
strength  or  direction.  A  current  alternating  peri- 
odically. 

Periodicity. — The  state  of  having  regular  periods  in 
changes.  The  rate  of  succession  in  fixed  phases. 


182  ELECTRICAL  DICTIONARY 

Periodicity  of  Alternation. — The  rate  of  succession  of 
alternations  per  second  or  per  minute.  The  fre- 
quency. 

Peripheral  Speed.— The  rapidity  of  rotation  as  indi- 
cated by  a  point  on  the  circumference  of  a  revolv- 
ing wheel  or  cylinder. 

Peripheral  Velocity. — The  rate  of  peripheral  speed. 

Peripheratic  Region. — A  region  embracing  other  re- 
gions within  itself. 

Permanency,  Electric. — In  electric  current  conductors 
the  power  to  retain  conductivity  unaffected  by 
lapse  of  time. 

Permanent  Intensity  of  Magnetization. — The  inten- 
sity of  a  permanent  magnetization  produced  in 
hard  steel,  in  contrast  to  that  temporarily  pro- 
duced in  soft  iron. 

Permanent  Magnet. — A  term  applied  to  a  hardened 
steel  magnet  possessing  high  magnetic  retentivity. 

Permanent-Magnet  Voltmeter. — A  voltmeter  which 
under  the  united  action  of  a  coil  and  a  permanent 
magnet  against  the  pull  of  a  spring  measures  dif- 
ferences of  potential  by  means  of  the  movement  of 
a  magnetic  needle. 

Permanent  Magnetism. — Magnetism  which  permanent 
magnets  possess. 

Permanent  Magnetization. — A  term  signifying  mag- 
netism caused  in  a  body  of  hard  iron  or  steel  when 
subjected  to  the  influence  of  a  magnetic  field. 
Magnetization  existing  in  a  permanent  magnet. 

Permeating. — The  penetration  of  magnetic  flux.  The 
close  interstitial  permeation  of  a  magnetizable 
mass. 


ELECTRICAL  DICTIONARY  183 

Permissivity. — Permittivity. 

Perpendicular. — A  line  at  right  angles  to  a  given  line 
or  surface. 

Personal  Equation. — An  er^or  of  observation  peculiar 
to  the  individual  and  due  to  his  optical  or  mental 
condition. 

Petticoat  Insulator. — An  insulator  having  at  its  lower 
end  a  deep  groove  resembling  a  petticoat.  A  single 
cup  telephone  or  telegraph  insulator. 

Phase. — The  interval  of  time  elapsing  from  the  time 
a  particle. moves  through  the  middle  point  of  its 
course  to  the  instant  when  the  phase  is  to  be 
stated ;  exhibited  in  wave,  oscillating  and  simple 
harmonic  motion.  One  complete  oscillation. 

Phase  Indicator. — An  instrument  which  indicates  when 
the  pressure  of  an  alternator  is  in  phase  with  that 
of  the  circuit  it  is  to  be  connected  with.  A  syn- 
chronizer. 

Phase  of  Vibration. — The  position  of  the  molecules  in 
motion  in  a  vibration  at  any  moment  of  time  pend- 
ing the  wave  period  as  contrasted  with  their  mean 
position. 

Phase-Splitter. — An  instrument  whose  function  is  to  so 
affect  an  incoming  alternating  current  that  when  it 
passes  out  again  it  does  so  in  different  branches 
and  as  a  number  of  currents  of  different  phase. 
An  instrument  serving  to  cause  difference  of  phase 
in  currents  by  which  a  single  phase  induction- 
motor  is  enabled  to  start  itself. 

Phase  Splitting. — The  act  of  causing  an  alternating 
current  to  split  up  into  a  number  of  currents  dif- 
fering in  phase. 


184  ELECTRICAL  DICTIONARY 

Phase  Transformation.  —  A  change  of  phase  effected  by 
means  of  a  transformer  which  transforms  two 
phase  currents  into  three  phase  currents  or  the 
reverse. 

Phase-  Windings.  —  The  individual  windings  on  a  poly- 
phase motor's  armature. 

Phenomenon.  —  Any  appearance  or  thing  visible  in 
nature  or  the  knowledge  of  the  existence  of  which 
is  acquired. 

Phone.  —  An  abbreviation  for  telephone.  A  telephone 
communication. 

Phone.  —  To  communicate  by  telephone. 

Phonic  Wheel.  —  A  single  form  of  small  motor  consist- 
ing of  a  toothed  wheel  of  soft  iron  and  operated 
in  synchronous  rotation  by  electric  excitation  pro- 
duced over  a  telegraphic  line,  and  used  in  the  syn- 
chronous multiplex  telegraph  system  of  Delaney. 

Phonograph.  —  An  instrument  which  records  and  re- 
peats speech  or  sounds. 

Phonograph  Record.  —  A  record  of  speech  or  sounds 
taken  by  the  phonograph. 

Phonoplex  Telegraphic-Receiver.  —  A  particular  kind  of 
telephone  receiver  used  in  connection  with  phono- 
plex  telegraphy,  which  is  affected  by  short  cur- 
excitations  ;  but  not  by  prolonged  ones. 


Phonoplex  Telegraphy.  —  Double  telegraphic  transmis- 
sion over  a  single  wire  without  interruption;  ef- 
fected by  the  superposition  of  telephonic  currents 
upon  common  Morse  currents  which  set  a  modified 
telephonic  receiver  in  action,  thus  obtaining  simul- 
taneous transmission. 


ELECTRICAL  DICTIONARY  185 

Phosphorescence. — The  capacity  to  exhibit  faint  light 
without  sensible  heat. 

Phosphorescent  Glow. — Phosphorescent  light  given  out 
by  the  residual  gas  in  a  vacuum  chamber  for  a  few 
moments  after  the  electric  charge  leaves  it. 

Photo-Chemical. — Pertaining  to  photo-chemistry. 
Photochemistry. — The  science  treating  of  the  chemical 
action  of  light. 

Photo-Electric. — Pertaining  to  the  united  action  of 
light  and  electricity. 

Photo-Electric  Cell. — A  cell  having  the  capacity  to 
cause  difference  of  potential  when  its  opposed  sur- 
faces are  unequally  exposed  to  light. 

Photo-Electric  Impulsion  Cell. — A  photo-electric  cell 
whose  sensibility  to  light  has  been  impaired;  but 
which  can  be  re-established  by  gentle  mechanical 
agitation  or  by  electro-magnetic  excitation. 

Photo-Electricity. — A  variation  of  electric  potential  re- 
sulting from  light  action. 

Photo-Engraving. — Engraving  done  by  means  of  light. 

Photo-Fluoroscopy. — An  image  photographically  pro- 
duced upon  a  fluoroscopic  screen. 

Photographic  Negative. — An  image  the  lights  and 
shadows  of  which  are  the  opposite  of  those  of  the 
original. 

Photographic  Positive. — An  image  the  lights  and 
shadows  of  which  correspond  to  those  of  the 
original. 

Photometer. — An  apparatus  employed  to  determine  the 
intensity  of  the  light  emitted  by  a  specified  light 
or  by  any  source  of  illumination. 


186  ELECTRICAL  DICTIONARY 

Photometer  Bar. — A  photometer  in  which  the  lights  to 
be  compared  are  placed  at  or  opposite  to  the  ends 
of  a  bar  or  scale  of  certain  length,  generally  60 
to  100  inches,  the  bar  having  a  photometer  screen 
which  indicates  the  relation  of  the  intensity  of  the 
lights  compared  by  the  distance  of  the  screens 
from  their  sources. 

Photometer  Bench. — A  photometer  bar  with  accom- 
panying photometric  apparatus  or  without  it. 

Photometer  Box. — A  box  having  the  light  excluded  and 
in  which  the  photometer  screen  is  put. 

Photometer  Disc. — A  photometer  screen. 

Photometer,  Electric. — An  instrument  serving  by 
means  of  electricity  to  measure  the  intensity  of 
light. 

Photometer  Screen. — A  -screen,  opaque  or  transparent, 
serving  in  a  photometer  to  measure  the  intensity 
of  light;  the  two  illuminations  to  be  compared 
being  projected  upon  it. 

Photometric. — Pertaining  to  a  photometer. 

Photophone. — An  instrument  serving  to  transmit  sound 
along  a  ray  of  light  in  place  of  a  conducting  wire. 

Photophore. — An  instrument  used  for  making  examina- 
tions of  the  cavities  of  the  body  by  means  of  a 
small  incandescent  lamp  adjusted  in  a  tube  with 
a  convex  lens  and  concave  mirror. 

Physical  Change. — Any  modification  in  the  forms  of 
matter  occurring  by  reason  of  a  re-adjustment 
of  its  molecular  assemblage  without  forming 
new  molecules;  in  contradistinction  to  chemical 
changes. 

Physical. — Pertaining  to  nature. 


ELECTRICAL  DICTIONARY  187 

Piano,  Electric. — A  piano  played  by  means  of  an  elec- 
tric motor  or  electro-magnets,  which  excite  the 
mechanism  controlling  the  hammers  which  strike 
the  strings. 

Pickle. — An  acid  solution  serving  to  clean  metallic  sur- 
faces before  electro-plating. 

Pile. — A  voltaic  or  galvanic  battery.  A  name  given  to 
batteries  only  which  have  plates  superimposed  and 
not  containing  vessel;  the  Dry  Pile,  for  instance, 
or  Volta's  Pile. 

Pilot  Lamp. — A  lamp  traversely  connected  to  a  dy- 
namo's terminals  and  serving  to  indicate  about 
what  pressure  it  is  producing.  A  lamp  employed 
on  a  central  station  dynamo  to  indicate  by  the 
intensity  of  the  light  emitted,  the  difference  of 
potential  at  the  terminals  of  dynamo. 

Pilot  Motor. — A  diminutive  motor  which  leads  or  sets 
in  operation  a  working  one.  A  small  motor  ar- 
ranged to  actuate  the  controller  of  a  large  motor. 

Pipe  Conduit. — A  conduit  consisting  of  metallic  pipes 
incased  in  or  lined  with  a  cementing  compound. 

Pitch. — The  distance  from  center  to  center  of  any  two 
adjacent  teeth  of  gearing  measured  on  the  pitch- 
line.  The  distance  measured  on  a  line  parallel  to 
the  axis,  between  two  adjacent  threads  of  a  screw. 
The  succession  of  musical  tone  vibrations.  The 
frequency  of  a  tone  produced  electrically.  The 
distance,  on  dynamo  armature,  between  successive 
corresponding  conductors.  The  number  of  coils  in 
which  advance  should  be  made  in  effecting-  end 
connections  between  the  coils  of  an  armature  wind- 
ing divided  into  segments. 


188  ELECTRICAL  DICTIONARY 

Pitch  Line. — A  line  encircling  the  surface  of  an  arma- 
ture through  the  center  of  the  inductors'  length, 
which  are  put  thereon. 

Pith. — A  light  and  soft  spongy  substance  forming  the 
central  part  of  exogenous  trees  and  plants. 

Pith  Balls. — Balls  made  of  pith  and  employed  in  the 
construction  of  electroscopes  and  for  other  pur- 
poses in  static  electricity. 

Pith-Ball  Electroscope. — An  electroscope  the  indica- 
tions of  which  are  shown  by  the  attractions  and  re- 
pulsions of  pith  balls. 

Planimeter. — An  instrument  designed  to  measure  by 
mechanical  means,  and  at  once,  the  area  of  any 
plane  figure  drawn  on  paper,  and  so  contrived  that 
when  the  tracer  has  passed  over  the  irregular  out- 
line of  a  figure  the  index  shows  the  area  of  the 
figure. 

Plant. — The  fixtures,  tools  and  machinery  necessary  to 
carry  on  any  mechanical  business.  An  installation. 

Plant  Efficiency. — The  efficiency  of  an  electric  plant. 
The  efficiency  of  a  plant  and  which  is  to  be  dis- 
tinguished from  the  distribution  system  by  which 
it  may  be  operated  or  which  it  operates. 

Plant  Efficiency  of  Motor. — The  efficiency  of  motor 
in  a  plant  considered  apart  from  the  system  with 
which  it  is  connected. 

Plastic. — Capable  of  being  moulded,  formed  or 
modeled. 

Plastic  Rail-Bond. — A  rail-bond  on  railroads  where 
sodium  amalgam  or  other  conducting  substance  is 
applied  in  plastic  form  in  order  to  obtain  contact 
of  rail  ends. 


ELECTRICAL  DICTIONARY  189 

Plate  Condenser. — A  static  condenser  having  a  flat 
piece  of  glass  for  dielectric.  Two  circular  brass 
plates  mounted  on  Insulated  supports  and  ar- 
ranged to  be  moved  towards  or  away  from  each 
other ;  between  them  being  a  plate  of  glass  or  other 
dielectric,  the  apparatus  being  used  to  illustrate  the 
principle  of  the  electric  condenser. 

Plated.^Covered  with  a  metallic  coating  by  the  pro- 
cess of  electro-plating. 

Plating. — A  word  signifying  electro-plating. 

Plating  Dynamo. — A  dynamo  which  furnishes  the  cur- 
rent employed  in  electro-plating. 

Platinoid. — An  alloy  of  copper,  nickel,  zinc  in  the  pro- 
portions of  german  'silver  with  1  or  2  per  cent  of 
tungsten  and  useful  for  its  resistive  qualities. 

Platinum. — A  metal  of  the  color  of  silver  with  a  specific 
gravity  of  20,  which  may  be  increased  by  heat  and 
pressure  to  21.5.  It  is  heavier  than  iron,  under- 
goes no  alterations  in  the  air,  resists  acids,  is  very 
ductile  and  is  the  heaviest  and  least  expansible  of 
the  metals. 

Platinum  Alloy. — Ordinarily  an  alloy  of  platinum  and 
silver. 

Platinum  Black. — Metallic  platinum  in  the  form  of  a 
black  powder  obtained  by  decomposing  a  weak  so- 
lution of  chloride  of  platinum  by  the  agency  of 
galvanism,  and  much  used  in  chemical  experi- 
ments. 

Platinum  Fuse. — A  slender  wire  of  platinum  raised  to 
incandescence  by  the  passage  of  an  electric  current 
and  used  to  explode  a  charge  of  powder. 

Platinum-Iridium  Alloy. — An  alloy  of  platinum  and  iri- 


190  ELECTRICAL  DICTIONARY 

dium  valuable  for  its  low  temperature-coefficient 
of  resistance  and  hence  often  used  for  resistance 
coils  in  electrical  instruments. 

Platinum  Lamp. — A  lamp  equipped  with  a  platinum  in- 
candescent filament. 

Platinum-Silver  Alloy. — An  alloy  of  platinum  and  sil- 
ver, one  and  two  parts  respectively,  and  possessing 
a  low  temperature  coefficient  of  resistivity. 

Plug  Cut-Out. — A  cut-out  which  uses  fuse  plugs. 

Plug  Resistances. — Separate  resistances  introduced  into 
the  circuit  by  removing  plugs.  The  resistances  per- 
taining to  the  common  resistance  box. 

Plugging. — The  employment  of  plugs  in  completing  a 
circuit.  The  making  of  connections  in  a  switch- 
board by  introducing  plugs  into  the  jacks. 

Plunge  Battery. — A  battery  the  plates  of  which  are  so 
arranged  as  to  be  immersed  in  the  battery  cups  or 
cells  when  the  battery  is  to  be  used  and  withdrawn 
and  supported  out  of  the  cups  or  cells  when  not  in 
use,  thereby  obviating  waste  'of  the  plates  by  stand- 
ing in  the  solution. 

Plunger  Switch. — A  switch  whose  operating  lever  cylin- 
der is  surrounded  by  a  bushing  in  the  switchboard 
in  order  that  contacts  may  be  made  or  broken  on 
reverse  side  of  board. 

Plus  Charge. — A  positive  charge. 

Pneumatic. — Pertaining  to  pneumatics. 

Pneumatics. — That  branch  of  science  which  treats  of 
the  mechanical  properties  of  air  and  other  elastic 
fluids. 

Pocket  Galvanometer. — A  galvanometer  adapted  to 
pocket  use. 


ELECTRICAL  DICTIONARY  191 

Poggendorff  's  Voltaic  Cell. — The  Grenet  cell. 

Points  of  Compass. — The  thirty-two  points  into  which 

a  compass  card  is  divided  at  equal  intervals  around 

its  periphery. 

Polar. — Pertaining  to  a  pole. 

Polar  Bore  of  Field  Frame. — The  hollow  bored  into  a 
field  frame  to  receive  an  armature. 

Polar  Relay. — A  relay  employed  in  telegraphy  and 
which  has  a  normally  polarized  armature,  thus  dif- 
fering from  a  neutral  relay  the  condition  of  whose 
armature  normally  is  magnetically  neutral. 

Polar  Surface  of  Magnet. — The  surface  of  a  magnetic 
substance  through  which  the  magnetic  flux  passes 
in  or  out.  The  surfaces  either  of  one  or  both  of  a 
magnet's  poles. 

Polar  Tips. — An  addition  made  of  iron  to  the  field 
magnet  pole  piece  of  a  dynamo-electric  machine. 

Polarity. — That  quality  of  a  body  in  virtue  of  which  it 
exhibits  opposite  properties  in  opposite  directions. 
The  possession  of  poles. 

Polarity  Indicator. — An  instrument  employed  to  indi- 
cate the  polarity  of  a  magnet  or  the  direction  of  a 
current. 

Polarization  of  Electrolyte. — A  supposed  arrangement 
of  molecular  assemblage  in  which  the  positive  poles 
of  any  one  assemblage  face  the  negative  plate, 
whilst  their  negative  poles  face  the  positive  plate. 

Polarization  of  Light. — The  state  of  a  ray  of  light  in 
which  the  ether-vibrations  producing  the  light  are 
confined  to  a  single  plane;  the  plane  called  "plane 
of  polarization"  being  perpendicular  to  it. 


192  ELECTRICAL  DICTIONARY 

Polarization  of  Voltaic  Cell. — An  accumulation  of  gas 
— hydrogen  usually — on  the  surface  of  a  voltaic 
cell's  negative  element. 

Polarized  Armature. — An  armature  possessing  polarity 
exclusive  of  that  communicated  by  the  working 
current. 

Polarized  Bell. — An  electro-magnetic  bell  equipped 
with  a  polarized  armature. 

Polarized  Indicator. — An  electro-magnetic  indicator 
provided  with  a  polarized  armature. 

Polarized  Relay. — A  telegraphic  relay  which  instead 
of  having  a  common  soft  iron  armature  is  provided 
with  one  permanently  magnetized. 

Polarizing  Current. — A  current  which  causes  polar- 
ization. 

Pole  Armature. — An  armature  whose  coils  are  wound 
on  separate  poles  projecting  radially  all  around 
the  periphery  of  its  central  hub  or  disc,  or  project- 
ing internally  from  a  ring-like  frame,  their  ends 
facing  the  field  magnet. 

Pole  Changer. — An  automatic  vibrating  or  oscillating 
contact-breaker  or  switch  which,  when  it  moves, 
reverses  the  direction  of  a  current  from  a  battery 
or  any  other  current  source — whose  direction  is 
fixed — as  such  current  passes  through  a  conductor. 

Pole-Pieces  of  Dynamo  or  Motor. — The  terminations  of 
the  cores  of  electro-magnets,  or  of  permanent  mag- 
nets, these  terminations  having  various  shapes, 
sometimes  quite  large  as  compared  with  the  core 
proper  of  the  magnet. 

Pole  Shoe. — An  iron  or  steel  plate  constituting  the  pole- 
piece  of  a  field  magnet  upon  which  it  is  mounted, 
and  employed  sometimes  to  support  a  field  coil. 


ELECTRICAL  DICTIONARY  193 

Pole  Tips. — (See  polar  tips.) 

Poles  of  Magnetic  Intensity. — The  location  of  highest 
magnetic  force  on  the  surface  of  the  earth;  one 
such  pole  being  in  Siberia,  another  in  about  lati- 
tude 52  degrees  N.,  longitude  92  degrees  W. 

Polishing  Bob. — A  disc  of  hard  wood  having  on  its  pe- 
riphery a  rim  of  leather  serving  when  rapidly  ro- 
tating upon  a  shaft,  and  by  means  of  fine  emery  to 
polish  articles  preparatory  to  electro-plating. 

Polycylic  System. — A  mutiphase  system. 

Polyphasal  Coupling  of  Magnetic  Circuits. — The  inter- 
linking of  magnetic  circuits  which  are  traversed  by 
polyphase  magnetic  fluxes. 

Polyphase. — Having  many  phases.    Having  more  than 

one  phase. 
Polyphase  Alternator. — An  alternator  which  furnishes 

polyphase  currents. 
Polyphase  Apparatus. — Apparatus  which  is  worked  by 

polyphase  currents. 

Polyphase  Armature. — An  armature  which  is  wound  in 
a  manner  to  produce  polyphase  currents,  or  which 
is  worked  by  them. 

Polyphase  Asynchronous  Motor. — An  asynchronous 
motor  which  is  worked  by  multiphase  currents. 

Polyphase  Currents. — A  term  signifying  groups  of  al- 
ternating currents  which  constantly  differ  from 
each  other  by  a  constant  proportion  of  periods  of 
alternation,  and  adapted  for  operating  polyphase 
motors. 

Polyphase  Dynamo. — A  polyphase  generator. 

Polyphase  Generator. — An  alternator  which  sends  out 


194  ELECTRICAL  DICTIONARY 

alternating  currents  having  a  fixed  difference  in 
phase. 

Polyphase  Inductor-Alternator. — An  inductor-alterna- 
tor adapted  to  the  production  of  polyphase  cur- 
rents. 

Polyphase  Motor. — A  motor  driven  by  polyphase  cur- 
rents. 

Polyphase  Synchronous-Motor. — A  synchronous  motor 
driven  by  polyphase  currents. 

Polyphotal  Arc-Light  Regulator. — A  regulator  adapt- 
able for  service  in  series  connected  arc  lamps. 

Poncelet. — A  term  signifying  a  unit  of  operative  en- 
ergy equal  to  100  kilogramme-metres  per  second. 

Porcelain. — A  fine  variety  of  earthenware  valuable  for 
insulating  purposes. 

Porcelain  Insulator. — An  insulator  made  of  porcelain 
and  used  to  support  a  wire. 

Porosity. — The  quality  or  state  of  having  pores  or  inter- 
stices. 

Porous  Cell. — A  jar  of  pipe  clay,  unglaze^1  earthenware 
or  other  material  of  like  character  usod  in  voltaic 
cells  to  keep  two  liquids  separate  and  at  same  time 
permit  electrolysis  and  electrolytic  induction. 

Porret's  Phenomenon. — An  increase  in  the  diameter  of 
a  nerve  produced  by  the  positive  pole  of  a  voltaic 
circuit  m  contact  with  the  tissue  and  in  proximity 
to  the  nerve  while  the  other  pole  is  connected  to 
another  part  of  the  body. 

Portable  Igniting  Device. — A  portable  device  employed 
for  electrically  lighting  gas  or  charges  of  powder 
and  other  explosives  used  in  mining. 


ELECTRICAL  DICTIONARY  195 

Portable  Tachometer. — A  speed  indicator  which  is  port- 
able. 

Portative  Power  of  Magnet. — The  power  possessed  by  a 
magnet  to  sustain  a  weight  by  the  attraction  of  its 
armature. 

Positive  Brush  of  Dynamo. — The  brush  out  of  which 
passes  the  current  generated  in  the  armature  of  a 
dynamo. 

Positive  Brush  of  Motor. — The  brush  connected  with 
the  positive  terminal  of  an  operating  source. 

Positive  Bus-Bars. — Bus-bars  connected  with  a  dyna- 
mo 's  positive  terminal. 

Positive  Carbon. — That  carbon  contained  in  a  voltaic 
arc  and  which  delivers  the  current  into  the  are. 

Positive  Currents. — The  currents  which  deflect  the 
needle  to  the  left,  in  the  single  needle  telegraph 
system. 

Positive  Electrode. — The  electrode  which  is  connected 
with  the  positive  pole  of  a  source. 

Positive  Feeders. — The  lead  or  wire  in  a  set  of  feeders 
which  is  connected  to  the  positive  terminal  of  the 
generator. 

Positive  Plate  of  Storage  Cell. — A  storage  cell  plate 
which  by  the  action  of  a  charging  current  becomes 
coated  with  a  layer  of  lead  peroxide.  The  plate  of 
a  storage  cell  which  becomes  the  positive  pole  of 
the  cell  on  discharging  by  reason  of  being  con- 
nected with  the  positive  terminal  of  a  charging 
•source. 

Positive  Plate  of  Voltaic  Cell. — A  voltaic  couple 's  elec- 
tro-positive element.  The  plate,  which  constitutes 


196  ELECTRICAL  DICTIONARY 

the  negative  pole  of  a  cell  above  the  surface  of  the 
electrolyte. 

Positive  Pole. — The  north  pole  in  a  magnet,  or  the  pole 
from  which  lines  of  force  are  assumed  to  emerge 
into  the  air. 

Positive  Rotation. — A  rotation  the  motion  of  which  is 
from  left  to  right. 

Positive  Side  of  Circuit. — The  side  of  a  circuit  which, 
if  an  observer  stood  girdled  by  the  current  with 
his  head  in  the  positive  side,  he  would  see  the  cur- 
rent pass  around  him  from  his  right  toward  his 
left  hand. 

Positive  Wire. — The  wire  connected  with  the  positive 
pole  of  any  arrangement  or  device  which  will  pro- 
duce an  E.  M.  F. 

Potential  Dynamometer. — A  device  or  apparatus  adapt- 
ed for  measuring  electric  potential  differences. 

Potential,  Electric.— The  ability  to  perform  electric 
work. 

Potential  Energy. — The  capacity  for  doing  work.  Po- 
tential chemical  energy  latent  in  an  elementary 
substance  which,  in  combination  with  some  other 
element  for  which  it  has  an  affinity,  becomes  liber- 
ated as  actual  energy  for  the  performance  of  work. 

Potential  Galvanometer. — A  galvanometer  which  is 
wound  with  fine  German  silver  wire  in  order  to  ob- 
tain high  resistance  and  used  for  determining  po- 
tential difference. 

Potential  Gradient. — A  line  which  represents  the  drop 
of  potential  in  a  circuit. 

Potential  Conductors. — The  ratio  between  the  volume 
of  current  in  a  conductor  and  its  capacity.  The 


ELECTRICAL  DICTIONARY  197 

property  possessed  by  a  conductor  to  perform  elec- 
tric work  when  approached  by  an  electric  charge. 

Power. — Activity.  The  rate  of  activity,  of  performing 
work,  or  of  exerting  energy ;  the  practical  unit  of 
electric  power;  being  the  volt,  ampere  or  watt,, 
equal  to  10  ergs  per  second. 

Power  Cable. — A  cable  through  which  electric  power  is 
transmitted. 

Power  Circuits. — Circuits  through  which  electric  power 
is  transmitted. 

Power  Factor. — The  relation,  in  an  alternating-current, 
conductor  or  circuit,  of  the  true  watt  to  the  ap- 
parent volt  amperes. 

Power-Factor  of  Transformer. — The  relation,  under  a 
specified  load,  of  the  watts  taken  up  by  a  trans- 
former to  the  watts  delivered  from  the  trans- 
former. 

Power  Generator. — An  alternating  current  generator 
employed  at  a  telephone  exchange. 

Power-House. — A  house  in  which  the  plant  of  an  elec- 
tric power  system  of  distribution  is  located. 
Power-Meter. — A  watt-meter. 

Power-Wire  of  Monocyclic  System. — In  a  monocyclic 
system  a  wire  which  furnishes  the  current  to  oper- 
ate triphase  electric  motors. 

Practical  Solenoid. — A  term  employed  to  distinguish 
the  ordinary  from  the  ideal  solenoid. 

Practical  Units. — A  system  of  units  based  on  the  abso- 
lute system  of  units,  except  that  multiples  of  the 
original  fundamental  units  of  lengths,  mass  and 
time  have  been  taken  as  the  base  of  the  new  system, 


198  ELECTRICAL  DICTIONARY 

and  they  consist  of  the  centimetre-gramme-second 
units. 

Presbyopic. — Far-sighted. 

Pressure,  Electric. — Electro-motive  force  or  potential 
difference ;  an  inaccurate  term. 

Pressure  Equalizer. — A  device  which  maintains  auto- 
matically a  uniform  pressure,  under  different  loads, 
at  the  terminals  of  a  storage  battery.  A  device  used 
in  a  system  of  electric  distribution  to  regulate  the 
pressure  and  keep  it  uniform. 

Pressure  Indicator. — An  instrument  which  serves  to  in- 
dicate the  electric  pressure  in  a  circuit.  A  volt- 
meter. 

Pressure  Recording-Gauge. — A  recording  voltmeter.  A 
recording  steam  or  water  gauge. 

Pressure  Wires. — Copper  wires  communicating  with  a 
central  station  from  junctions  between  the  feeders 
and  the  mains  and  serving  to  indicate  at  central 
station  the  pressure  on  the  mains. 

Primary  Battery. — A  single  electric  source  comprising 
several  separate  primary  cells. 

Primary  Coil  Transformer. — The  coil  which  receives  the 
current  to  be  transformed. 

Primary  Currents. — Currents  which  pass  through  a  pri~ 
mary  circuit. 

Primary  Cut-Out. — A  cut-out  used  in  a  primary  circuit. 

Primary  Electric  Clock. — A  name  signifying  "control- 
ling clock." 

Primary  Electromotive  Force. — Electromotive  force  ap- 
plied to  a  transformer's  primary  coil. 

Primary  Fuse  Box. — A  fuse  box  used  in  a  transformer's 
primary  circuit  or  in  that  of  an  induction  coil. 


ELECTRICAL  DICTIONARY  199 

Primary  Impedance. — The  impedance  of  a  transformer's 
primary  coil  or  that  of  an  induction  machine. 

Primary  Plate  of  Condenser. — The  plate  of  a  condensing 
transformer  which,  when  containing  the  inducing 
charge,  induces  in  the  secondary  plate  a  charge  of 
different  potential. 

Prime  Magnetic  Flux. — Magnetizing  force  and  which 
is  different  from  magnetic  induction.  The  flux, 
which  the  prime  magneto-motive  force  produces  in 
a  ferric  circuit;  and  differing  from  the  induced 
magneto-motive  force. 

Prism  Error  of  Compass. — An  error  occurring  in  a  com- 
pass arising  from  an  incorrect  disposition  of  the 
prism  as  referred  to  the  compass  card. 

Probe,  Electric. — A  surgeon's  probe  contrived  to  indi- 
cate by  the  closing  of  an  electric  circuit  the  pres- 
ence of  a  bullet  or  any  other  metallic  object  in  the 
human  body. 

Process  of  Carbonization. — A  method  by  which  suitable 
materials  are  carbonized. 

Production  of  Cold  by  Electricity. — The  reduction  of 
temperature  at  a  thermo-electric  junction  attending 
the  absorption  of  energy,  which  follows  the  passage 
of  an  electric  current  across  the  junction  in  a  cer- 
tain direction. 

Production  of  Electricity  by  Light. — Electric  difference 
of  potential  effected  by  the  action  of  light. 

Projecting  Power  of  Magnet. — The  distance  at  which 
attraction  or  repulsion  is  effected  by  a  magnet. 

Projection  Arc-Lamp. — An  arc  lamp  adopted  to  pro- 
ject for  searchlight  purposes. 


200  ELECTRICAL  DICTIONARY 

Projector  Electric. — A  projector  at  whose  focus  an  elec- 
tric arc  light  is  employed. 

Projection  Armatures. — Armatures  in  which  depressions 
are  made  of  sufficient  width  to  leave  a  projection 
in  the  armature  surface,  therein  differing  from  the 
narrow  slotted  tunnel  armatures. 

Prony  Brake. — A  device  used  to  measure  the  power  ap- 
plied to  a  rotating  shaft  by  applying  a  clamping 
device  to  the  shaft  or  pulley.  A  dynamometer. 

Proof-Plane. — A  small  conductor  carried  at  the  end  of 
an  insulating  handle  and  used  to  collect  electricity 
by  contact  from  objects  electrostatically  charged, 
the  charge  received  being  then  measured. 

Proportional  Coils. — Pairs  of  resistance  coils,  represent- 
ing ordinarily  a  resistance  of  10,  100  and  1,000 
ohms  each,  serving  as  proportional  arms  for  a 
bridge  or  a  balance;  used  in  the  box  of  Wheat- 
stone's  bridge. 

Proposed  Definition  for  2,000  Candle-Power  Arc. — An 
arc  whose  maintenance  will  require  450  watts. 

Propulsion,  Electric. — A  term  signifying  propulsion  by 
electric  power. 

Protection  of  Metals,  Electric. — A  method  by  which 
metals  are  prevented  from  corroding,  and  which 
consists  of  exposing  a  protecting  metal  to  the  cor- 
roding fluid,  which,  by  forming  with  the  surround- 
ing fluid  the  positive  element  of  a  voltaic  couple, 
is  subjected  alone  to  the  corrosive  action,  and 
thereby  protects  from  corrosion  any  metal  with 
which  it  has  been  placed. 

Protection  of  Ship's  Sheathing,  Electric. — A  method 
for  preventing  the  corrosion  from  water  of  the  cop- 


ELECTRICAL  DICTIONARY  201 

per  sheathing  of  a  ship  by  fastening  pieces  of  zinc 
to  it. 

Protective  Sheath. — A  sheath  of  copper  introduced  be- 
tween the  primary  and  secondary  circuits  of  an  al- 
ternating current  transformer,  and,  being  con- 
nected to  the  earth,  it  becomes  grounded  if  the 
primary  coil  loses  its  insulation  before  it  can  leak 
to  the  secondary,  thus  protecting  the  secondary 
circuit  from  the  high  electro-motive  force  of  the 
primary  circuit. 

Public  Supply  Instruments. — Electric  meters  which 
serve  to  register  the  supply  of  current  to  consum- 
ers. 

Pull. — A  switch  for  closing  a  circuit  when  pulled  as 
distinguished  from  a  push  button. 

Pulley. — A  wheel  with  a  broad  rim,  mounted  on  a  shaft, 
to  which  the  driving  power  is  imparted  by  means 
of  a  belt. 

Pull-Off. — An  insulator  which  serves  to  hold  the  trol- 
ley wire  in  its  proper  place  over  curves  in  the 
track. 

Pulsating  Motor. — The  early  type  of  motor  depending 
upon  reciprocating  motion  in  its  armature  as  dis- 
tinguished from  the  ordinary  rotary  motion. 

Pulsatory  Magnetic-Field. — A  field  produced  by  pulsat- 
ing currents  and  by  induction;  such  field  can  pro- 
duce an  alternating  current. 

Pumping  of  Alternating- Current  Dynamo. — A  pulsa- 
tory movement  resulting  from  imperfect  synchron- 
ism and  observed  in  synchronously-running  alter- 
nating current  generators  or  motors. 

Pumping  of  Electric  Lights. — A  term  signifying  a  pe- 
riodical loss  or  gain  in  the  brilliancy  of  lights. 


202  ELECTRICAL  DICTIONARY 

Pupillary  Photometer. — A  photometer  whose  action  is 
contingent  upon  the  decrease  in  diameter  of  the 
pupil  of  the  eye,  which  is  exposed  to  the  intensity 
of  the  light. 

Push. — A  push  button. 

Push-Button. — A  switch  serving  to  close  a  circuit  by 
means  of  pressure  upon  a  button. 

Putting1  Straight. — The  restoration  to  their  proper 
conditions  of  wires  that  have  been  crossed. 

Pyrogravure. — A  process  of  decoration  by  the  means 
of  a  tool,  heated  electrically  or  by  other  means,  and 
applied  to  copper,  glass  or  wood. 

Pyro-Magnetic  Generator  or  Dynamo. — An  apparatus 
by  means  of  which  electricity  is  generated  directly 
from  the  heat  obtained  from  burning  fuel. 

Pyro-Magnetic  Motor. — A  motor  operated  by  the  alter- 
nation of  an  armature's  or  other  moving  member's 
attraction  and  release,  as  such  member,  or  section 
of  it,  becomes  more  or  less  paramagnetic  by  heat. 

Pyro-Magnetism. — The  development,  by  heat,  of  new 
magnetic  properties  or  alteration  of  magnetic  sen- 
sibility in  a  body. 

Pyrometer. — An  instrument  for  measuring  tempera- 
tures too  high  for  the  capacity  of  thermometers. 

Pyrometer,  Electric. — An  instrument  for  measuring 
high  temperatures  by  the  variations  in  electric 
resistance  exhibited  by  a  platinum  wire  exposed  to 
the  heat  which  is  to  be  measured. 


ELECTRICAL  DICTIONARY  203 

Q. 

Quad. — An  abbreviation  for  quadruplex;  an  abbrevia- 
tion for  the  quadrant,  used  as  the  unit  of  induct- 
ance. 

Quadrant. — A  length,  approximately  an  earth  quadrant 
and  equal  to  10.9  centimeters;  sometimes  applied 
to  the  unit  of  inductance.  The  henry. 

Quadripolar  Dynamo  or  Generator. — A  multipolar 
dynamo  which  has  four  field  magnet  poles. 

Quadripolar  Field. — A  field  created  by  four  magnet 
poles. 

Quadruplex  Circuit. — A  single  circuit  capable  of  hav- 
ing four  messages  transmitted  over  it  simultan- 
eously, two  in  one  direction  and  two  in  the  op- 
posite. 

Quadruplex  Telegraphy. — A  system  of  telegraphy  pro- 
viding for  the  transmission  of  messages  over  a 
quadruplex  circuit. 

Quadruplex  Telephony. — The  transmission  simultan- 
eously of  four  telephonic  messages,  two  in  one  di- 
rection and  two  in  the  opposite. 

Quadruplex  Re-entrant  Armature  Winding. — An  arma- 
ture having  four  separate  and  independently  re- 
entrant windings. 

Qualitative  Analysis. — Analysis  for  determining  the 
constituent  elements  of  a  compound  without  regard 
to  quantity. 

Quality  of  Radiation. — The  quality  of  radiation  as  re- 
ferred only  to  its  frequency  and  amplitude  of  vi- 
bration. 


204  ELECTRICAL  DICTIONARY 

Quantitative  Analysis. — That  method  of  analysis  which 
determines  the  proportional  quantity  of  each  of 
the  elements  which  make  up  a  compound. 

Quantity  Efficiency  of  Storage  Battery. — The  relation 
existing  between  the  number  of  ampere-hours  re- 
ceived from  a  storage  battery  to  the  number  sup- 
plied to  the  battery  in  charging  it. 

Quarter-Phase. — The  separation  by  a  quarter  period  of 

*         two  alternating  quantities. 

Quarter-Phase  Armature. — An  armature  of  the  poly- 
phase class,  serving  to  produce  quarter-phase  cur- 
rents. 

Quarter-Phase  Bar-Winding  for  Armature. — A  bar- 
winding  used  in  a  quarter-phase  generator's  arma- 
ture. 

Quega. — A  prefix  meaning  a  quintillion. 

Quick-Break. — A  break  in  a  current  effected  by  the 
employment  of  a  quick-break  switch. 

Quick-Break  Switch. — A  switch  by  means  of  which  a 
circuit  is  quickly  broken. 

Quickening  Solution. — A  solution  into  which  articles 
that  are  to  be  electro-plated  are  dipped  after  clean- 
ing immediately  prior  to  their  immersion  in  the 
plating  bath.  A  solution  of  salt  of  mercury. 

Quiet  Arc. — An  arc  devoid  of  noise. 

Quiet  Commutation. — Sparkless  commutation. 

Quivering  of  Magnetic  Field. — The  periodic  motions  of 
magnetic  flux  resulting  from  the  successive  com- 
mutations of  the  advancing  armature  coils  and 
manifested  under  the  leading  pole-piece  of  a  gen- 
erator or  the  trailing  pole-piece  of  a  motor. 


ELECTRICAL  DICTIONARY  205 

R. 

R.  P.  M. — An  abbreviation  meaning  revolutions  per 
minute. 

Raceway. — A  space  along  the  length  of  a  conduit  pro- 
vided for  the  ready  introduction  or  removal  of 
conductors. 

Racing  of  Dynamo. — Rapid  acceleration  of  speed  in  a 
dynamo-electric  machine  following  the  abrupt  re- 
moval of  its  load,  as,  for  instance,  when  a  belt 
breaks. 

Racing  of  Motor. — Rapid  acceleration  in  the  speed  of 
an  electric  motor,  following  the  abrupt  removal  of 
its  load. 

Rack-Rail-Incline  Electric  Railway. — A  method  by 
which  a  trolley  car  is  hauled  over  a  steep  grade  by 
means  of  a  rack-rail  used  as  in  the  ordinary  incline 
system. 

Radial  Truck. — A  support  of  a  triple-truck  design  for 
the  body  of  a  car,  the  car  resting  on  the  end  truck 
centers  in  a  manner  which  enables  the  trucks  to 
turn  freely  and  carry  the  middle  truck  between 
them. 

Radially-Laminated  Armature. — An  armature  core  in 
which  the  iron  is  made  up  of  light  discs,  supported 
on  the  shaft  in  a  suitable  manner. 

Radiate. — To  emit  or  send  out  in  direct  lines  from  a 
point  or  points ;  as,  to  radiate  heat. 

Radiation  Constant. — That  heat  which  is  lost  by  radi- 
ation in  a  given  length  of  time  when  the  tempera- 
ture of  the  body  from  which  the  heat  is  radiated 


206 


ELECTRICAL  DICTIONARY 


is  one  degree  higher  than  that  of  the  surrounding 
atmosphere. 

Radiation  of  Magnetic  Flux. — The  issue  of  magnetic 
flux  from  a  magnet's  north  seeking  pole. 

Radiator,  Electric. — A  radiator  electrically  heated  em- 
ployed for  heating  rooms  and  other  spaces. 
Radiograph. — A  picture  taken  by  the  X-rays  process. 

Radiometer. — An  instrument  which  comprises  four 
vanes  poised,  on  an  axis,  thus  enabling  it  to  rotate 
freely,  and  enclosed  in  a  sealed  and  glass  vessel  al- 
most completely  exhausted.  The  Crookes  radio- 
meter. t 

Radiophonic  Sounds.— Sounds  produced  by  the  direct 
action  of  radiated  energy  on  certain  bodies. 

Radophony. — The  production  of  sound  by  the  intermit- 
tent action  upon  a  body  of  a  beam  of  light. 

Rail-Bond,  Electric. — A  device  employed  to  obtain  good 
electrical  contact  between  the  ends  of  rails  in  order 
to  reduce  to  a  minimum  the  resistance  of  the  joints 
of  the  rails,  which  are  used  as  a  portion  of  the  re- 
turn circuit. 

Rail  Bonding. — Connecting  rails  in  such  manner  as  to 
obtain  close  electric  contact. 

Railroad,  Electric. — An  electric  railroad,  employing 
electric  motors  placed  upon  cars  or  locomotives  by 
means  of  which  they  are  propelled. 

Railway  Current-Controller. — A  style  of  switchboard 
serving  to  govern  the  output  of  an  electric  power 
house.  A  motor-controller  employed  on  railroads 
to  start,  stop  and  modify  the  speed  of  cars. 

Railway  Generator. — A  dynamo  electric  machine  em- 


ELECTRICAL  DICTIONARY  207 

ployed  in  systems  of  electric  railroads  to  generate 

the  current  required  for  operation. 
Railway  Line-Crossing. — Methods  adopted  to  support 

trolley  wires  where  two  or  more  cross  one  another 

at  points  along  the  line. 
Railway  Motor. — An  electric  motor  by  means  of  which 

electric  street  and  trolley  cars  are  propelled. 
Railway  Return  Circuit. — A  grounded  circuit  used  in 

trolley  systems  for  ground  return.     The  negative 

side  of  the  system  usually. 

Range  Indicating  System. — A  telegraphic  system  em- 
ployed on  men  of  war  whereby  the  distance  of  the 
targets  is  determined  by  the  range  finder  and  indi- 
cated at  the  guns. 

Rated  Candle-Power. — Nominal  candle-power. 

Ratio  Proportionate  Arms  of  Bridge. — A  term  applied 
to  the  proportionate  arms  of  a  Wheatstone  bridge. 

Ratio  of  Transformation. — The  relation  existing  be- 
tween electromotive  force  produced  at  an  induc- 
tion coil's  secondary  terminals  and  that  which  is 
impressed  on  the  primary  terminals. 

Ray. — A  line  of  light  or  heat  or  other  form  of  energy 
proceeding  from  a  radiant  or  reflecting  point. 

Reactance. — The  product  of  the  induction  by  the  angu- 
lar velocity  of  the  sinusoidal  current  which  passes 
through  it.  In  a  simple-harmonic  current  circuit, 
a  quantity,  the  square  of  which  added  to  the  square 
of  the  resistance,  gives  the  square  of  the  impend- 
ance. 

Reaction  Coil. — A  coil  of  high  self  induction  employed 
to  resist  the  intensity  of,  or  "choke"  alternating 
currents,  and  formed  of  insulating  wire  wound 


208  ELECTRICAL  DICTIONARY 

upon  a  laminated  or  divided  iron  core,  and  so 
shaped  as  to  afford  a  closed  magnetic  circuit. 

Reaction  Motor. — Induction  motor. 

Reaction  Principle  of  Dynamo-Electric  Machine. — A 
principle  of  the  dynamo  current  generator  provid- 
ing for  the  reciprocal  action  of  the  current  pro- 
duced in  the  armature  coils  and  the  field  coils  of  a 
continuous-current  dynamo-electric  machine, 
whereby  one  strengthens  the  other  until  the  cur- 
rent very  soon  reaches  its  full  strength. 

Reaction  Telephone. — A  style  of  telephone  equipped 
with  two  coils  of  insulating  wire,  one  being  placed 
on  the  disc  and  the  other  on  the  magnet  pole,  the 
coils  reacting  upon  each  other,  thus  producing  a 
stronger  effect. 

Reactive  Coil. — Reaction  coil. 

Reactive  Drop. — The  drop  occurring  in  a  circuit  result- 
ing from  reactance,  differing  thereby  from  the  drop 
due  to  ohmic  resistance. 

Real  Efficiency  of  Storage  Battery. — In  a  storage  bat- 
tery the  relation  existing  between  the  number  of 
watt-hours  taken  out  of  the  battery  and  those  put 
into  it  when  charging.  The  energy  efficiency  of  a 
storage  battery  as  distinguished  from  its  quantity 
or  ampere-hour  efficiency. 

Rebabbitting. — Renewing  the  Babbitt  metal  on  ma- 
chine bearings. 

Recalibration. — The  recalibration  of  an  instrument. 

Receiver. — An  instrument  for  receiving  messages  in 
telephony  and  telegraphy  and  also  a  term  applied 
to  the  receiving  instrument  of  a  gramophone  and 
graphophone. 


ELECTRICAL  DICTIONARY  209 

Receiving  End  of  Line. — The  end  of  a  line  where  the 
currents  are  received  as  opnosed  to  the  end  at 
which  they  are  transmitted. 

Receiving  Magnet. — Any  magnet  which  forms  part  of 
the  receiving  apparatus  employed  at  the  receiving 
end  of  a  telegraph  or  telephone  line.  A  relay. 

Receptacle. — A  device  for  the  reception  of  an  attach- 
ment plug  and  used  in  incandescent  lighting. 

Receptive  Device. — A  device  serving  to  receive,  trans- 
late, utilize  or  transform  energy. 

Reciprocal. — Quantities  which,  multiplied  together, 
produce  unity. 

Reciprocating  Motor. — A  motor  having  a  reciprocating 
action  or  one  moving  first  in  one  direction  and  then 
in  the  opposite. 

Recoil  Kick  or  Disruptive  Discharge. — A  reaction  re- 
sulting from  a  disruptive  discharge. 

Recorder  Ammeter. — An  ammeter  which  makes  a  per- 
manent record  of  its  indications. 

Recording  Meter. — An  electric  meter  which  records  its 
indications. 

Recording  Voltmeter. — A  voltmeter  which  makes  a  per- 
manent record  of  its  indications. 

Recording  Wattmeter. — A  wattmeter  which  records  its 
indications. 

Rectangular  Curve. — A  curve  with  outlines  approxi- 
mately conforming  to  a  rectangular  shape. 

Rectification  of  Alcohol,  Electric. — The  process  of  recti- 
fying or  purifying  alcohol  by  electricity. 

Rectified. — Commuted — Changed  as  regards  direction. 

Rectified  Currents. — Commuted  Currents. 


210  ELECTRICAL  DICTIONARY 

Rectifier. — A  commutator. 

Rectifying  Commutator. — A  commutator  that  commutes 
alternating  into  direct  currents. 

"Red"  Magnetism. — A  distinguishing  term  suggested 
by  the  two-fluid  theory  of  magnetism  and  applied 
to  the  magnetism  at  the  north  pole  of  a  magnet. 

Redressed  Currents. — Currents  changed,  as  regards  di- 
rection or  directions  by  a  commutator. 

Reduction  Gear. — A  gear  serving  to  reduce  the  speed 
of  a  street  car  below  that  of  its  driving  motor. 

Re-Entrant  Armature-Windings. — Armature-windings 
which  lead  back  to  their  point  of  departure. 

Refining  Electric. — The  electrolytic  refining  of  metals. 

Reflect. — To  throw  back  light,  heat  or  the  like  from  a 
surface. 

Reflecting  Galvanometer. — A  galvanometer  whose 
needle  deflections  are  read  by  means  of  an  image 
which  a  reflected  light  from  a  mirror  projects.  A 
mirror  galvanometer. 

Reflection. — The  throwing  back  of  light,  heat  or  the 
like  from  a  surface  at  an  equal  angle  to  that  at 
which  it  strikes  it. 

Refract. — To  break  the  natural  course  of  rays  in  an 
elastic  medium,  as  for  instance  the  refraction  of 
the  rays  of  light  as  they  pass  from  a  rare  into  a 
dense  medium. 

Refraction. — The  change  in  the  direction  of  a  ray  of 
light,  heat  or  electro-magnetism  when  it  enters 
obliquely  a  medium  of  a  different  density  from  that 
through  which  it  has  previously  moved. 

Refractory. — Difficult  of  fusion.  Not  readily  yielding 
to  heat ;  said  especially  of  metals. 


ELECTRICAL  DICTIONARY  211 

Regenerative  Cell. — A  cell  restored  to  the  performance 
of  its  proper  functions  of  producing  currents  by  a 
process  of  charging. 

Registering  Photometer. — A  photometer  which  registers 
the  chemical  action  of  light  as  distinguished  from 
one  which  registers  the  photometric  action. 

Regulating  Cell  for  Storage  Battery. — A  counter-elec- 
tromotive force  cell. 

Regulating  Lamp  Socket. — A  socket  provided  with  a 

device  having  a  switch  attached  and  which  serves 

to  vary  the  brilliancy  in  an  electric  incandescent 

lamp. 
Regulation  of  Dynamo. — The  maintenance  of  constancy 

in  the  current  or  pressure  of  a  dynamo  by  proper 

adjustment. 
Regulation  of  Motor. — The  maintaining  constant  of  the 

speed  or  the  torque,  or  both,  of  a  motor  by  proper 

adjustment.     „ 
Regulation  for  Dynamo. — A  device  serving  to  regulate 

a  dynamo. 
Regulator  for  Motor. — A  device  serving  to  regulate  a 

motor. 

Regulator  Magnet. — A  magnet  designed  to  effect  any 
required  regulation  automatically.  A  magnet 
whose  armature  moves  in  such  manner  as  to  auto- 
matically shift  the  commutator  brushes  to  a  posi- 
tion on  the  commutator  which  insures  the  preser- 
vation of  the  current  constant,  notwithstanding 
any  variation  of  resistance  in  the  external  circuit. 

Relative   Inductivity. — The   relation   existing  between 

the  inductivity  of  a  medium  and  that  of  a  vacuum. 

Relay. — A    telegraphic    receiving    instrument    which 


212  ELECTRICAL  DICTIONARY 

opens  and  closes  a  local  circuit  by  movements 
caused  by  the  impulses  of  currents  received. 

Relay  Bells. — Bells  connected  to  a  main  line  by  relay 
connection  for  acoustic  telegraphy.  The  system 
has  practically  fallen  into  disuse. 

Relay  Contact. — A  term  often  used  for  a  type  of  electro- 
magnetic instrument  which  serves  to  complete  a 
local  circuit  on  the  passage  of  a  current. 

Relief  Photometer. — A  form  of  photometer  in  which 
two  divisions  of  the  screen  are  placed  at  right 
angles  to  each  other  and  the  whole  screen  then 
appearing  as  a  single  plane  illumined  surface,  the 
quality  of  illumination  is  easily  determined. 

Reluctance. — Magnetic  resistance. 

Reluctivity. — The  reluctance  of  a  cube  of  matter  the 
edge  of  which  in  length  measures  one  centimeter. 

Reluctivity  Constants. — Constants  which  give  the  reluc- 
tivity of  iron  'or  steel  when  applied,  in  accordance 
with  a  formula,  to  their  magnetic  force. 

Remanent  Flux. — Residual  magnetism. 

Remanent  Magnetism. — A  term  used  for  residual  mag- 
netism. The  magnetism  in  a  core  after  the  exciting 
current  ceases  to  flow. 

Repeating  Relay. — In  telegraphy  a  relay  for  repeating 
the  signals  through  a  second  line. 

Repeating  Sounder. — In  telegraphy  a  sounder  which  re- 
peats a  message  into  another  circuit. 

Repeating  Telegraphic  Station. — A  Station  on  a  long 
telegraphic  line  occupying  a  position  between  the 
sections  into  which  the  line  is  divided  and  at  which 
the  currents  received  on  one  section  are  repeated 
into  the  other  section  by  means  of  a  repeater. 


ELECTRICAL  DICTIONARY  213 

Repeating  Telephone  Coil. — An  induction  coil  with  two 
equal  windings,  each  one  being  connected  to  a  tele- 
phone circuit,  thus  obtaining  close  inductive  asso- 
ciation. 

Repulsion,  Electric. — The  tendency  'which  exists  be- 
tween two  bodies  charged  alike,  to  mutually  repel 
each  other. 

Repulsion  Motor. — A  motor  receiving  its  power  through 
the  mutual  repulsion  of  electric  charges.  An  alter- 
nating-current motor  receiving  its  power  through 
the  mutual  repulsion  of  electric  charges.  An  al- 
ternating-current motor,  in  which,  by  means  of  a 
commutator  and  brushes,  the  armature  is  provided, 
for  the  time  being,  with  short  circuited  windings. 

Residual  Atmosphere. — The  minute  quantity  of  air  or 
other  gas  which  is  left  in  a  vessel  or  chamber  after 
it  has  been  practically  exhausted  by  a  pump  or 
'Otherwise. 

Residual  Charge. — The  charge  left  in  a  Leyden  jar 
after  disruptive  discharge. 

Residual  Magnetic-Flux. — The  residual  magnetism  re- 
maining after  magnetic  induction  ceases,  expressed 
in  lines  of  force  per  square  centimeter.  Magnetic 
flux  left  in  a  magnetic  circuit  after  the  disappear- 
ance of  the  magnetizing  force. 

Resilence. — Elasticity. 

Resin. — A  solid  inflammable  substance,  of  vegetable 
origin ;  a  non-conductor  of  electricity. 

Resistance. — That  property  of  an  electric  conductor  by 
which  it  opposes  the  passage  of  an  electric  current. 

Resistance  Box. — A  term  applied  to  a  box  which  con- 
tains graduated  resistance  coils. 


214  ELECTRICAL  DICTIONARY 

Eesistance  Bridge.— Electric  balance.  Wheatstone's 
balance. 

Resistance  Coil. — A  coil  of  wire  or  other  conductor  hav- 
ing the  capacity  to  offer  resistance  to  the  flow  of 
electricity.  A  coil  of  wire  employed  to  measure 
an  unknown  resistance  by  virtue  of  its  own  known 
resistance. 

Resistance  Losses. — Losses  caused  by  friction  in  the 
transmission  of  energy.  Losses  in  a  system  of  elec- 
trical distribution  occasioned  by  resistance. 

Resistance  of  Human  Body,  Electric. — Ohmic  resistance 
opposed  to  the  passage  of  an  electric  discharge  or 
current  by  the  human  body. 

Resistance  of  Human  Skin,  Electric. — The  ohmic  resis- 
tance offered  by  the  human  skin  to  the  passage  of 
an  electric  current. 

Resistance  of  Voltaic  Arc. — The  resistance  which  a  vol- 
taic arc  offers  to  the  passage  of  a  current. 

Resistance  Slide. — A  rheostat  provided  with  a  sliding 
contact  by  means  of  which  the  several  resistances 
or  coils  are  put  in  or  taken  out  of  a  circuit. 

Resistants. — Bodies  capable  of  resistance. 

Resisting  Torque. — The  torque  required  by  a  motor  to 
enable  it  to  move.  The  torque  of  retarding  forces. 

Resonator,  Electric. — An  open  electric  circuit  of  small 
dimensions  whose  ends  are  nearly  in  contact  and 
which,  when  subjected  to  the  influence  of  the  elec- 
tric resonance,  a  spark  produced  by  the  inductance 
of  the  resonator  passes  across  the  gap. 

Rest. — A  cessation  from  motion. 

Resultant. — A  force  which  is  the  joint  effect  of  two  or 
more  forces. 


ELECTRICAL  DICTIONARY  215 

Resultant  Induction. — The  magnetic  induction  in  a 
dynamo 's  armature  or  any  mass  of  magnetized  ma- 
terial which  is  the  resultant  of  the  inducing  effect 
of  several  components  of  magnetic  induction. 

Resultant  Magnetic  Field  of  Dynamo. — The  magnetic 
field  which  is  the  product  of  both  the  field  pro- 
duced by  the  field  magnets  and  the  current  passing 
through  the  armature  coils. 

Retardance. — The  limitation  of  a  telephone  circuit  with 
respect  to  the  transmission  of  sound  and  which  is 
equal  to  the  total  ohmic  resistance  and  total  ca- 
pacity of  the  line. 

Retarding  Coil. — Choking  Coil. 

Retarding  Disc. — A  disc  of  copper  mounted  on  a  rotat- 
ing shaft  so  arranged  as  to  cut  magnetic  flux,  which 
results  in  the  retardation  of  its  rotary  speed. 

Retardation  Coil. — Choking  Coil.  Retarding  coil.  In- 
duction coil. 

Retentiveness. — That  property  which  enables  steel  to 
retain  its  magnetism. 

Retentivity. — The  quality  of  retaining  magnetization 
or  of  resisting  demagnetization. 

Retort  Carbon. — Carbon  deposited  from  decomposition 
of  the  hydrocarbons  and  little  used  for  electric 
purposes  owing  to  its  extreme  hardness. 

Return  Circuit. — That  portion  of  a  circuit  by  which 
an  electric  current  returns  to  the  generator. 

Return  Feeders. — The  feeders  along  which  the  current 
passes  on  its  way  back  to  a  central  station.  The 
return  feeders  on  a  trolley  line  which  are  connected 
with  the  track.  Ground  feeders.  Negative  feed- 
ers. 


216  ELECTRICAL  DICTIONARY 

Return  Ground. — The  portion  of  the  ground  which 
serves  as  a  return.  The  ground-return. 

Return-Signal  Call-Box. — A  call-box  which  answers  a 
signal. 

Reversal. — A  change  of  direction. 

Reversal  of  Phase. — A  change  in  the  phase  of  a  current 
which  is  caused  either  by  the  reversal  of  the  cur- 
rent or  of  the  conductor  in  which  it  is  generated. 

Reversible  Electric  Motor. — A  motor,  the  direction  of 
whose  motion  can  be  easily  reversed.  A  motor 
constructed  in  a  manner  to  render  its  operation  as 
a  generator  practicable. 

Reversibility  of  Dynamo. — A  dynamo,  which  when 
traversed  by  an  electric  current,  can  operate  as  a 
motor. 

Reversing. — To  alter  a  direction  to  its  opposite. 

Reversing  a  Current. — Altering  a  current's  direction. 

Reversing  Controlling-Box. — A  controlling  box  by 
means  of  which  the  direction  of  a  motor's  rotation 
can  be  reversed. 

Reversing-Gear  of  Electric  Motor. — Apparatus  by 
means  of  which  a  motor's  direction  of  rotation  can 
be  reversed. 

Reversing-Handle  of  Car  Controller. — A  switch  handle 
attached  to  a  car  controller  and  serving  to  change 
its  direction  of  motion.  The  handle  of  the  emer- 
gency switch. 

Reversing  Key. — A  key  which,  when  inserted  in  the  cir- 
cuit of  a  galvanometer,  obtains  deflections  on  either 
side  of  its  scale.  A  key  whose  function  is,  when 
inserted,  to  reverse  the  current  given  out  to  a  cir- 
cuit. 


ELECTRICAL   DICTIONARY  217 

Rheostat. — An  apparatus  serving  to  change  the  resist- 
ance without  opening  a  circuit.  An  adjustable  re- 
sistance. 

Rheostat  Frame. — A  perforated  frame  in  which  the  sev- 
eral resistances  of  a  rheostat  are  enclosed. 

Rheostat  Panel. — A  switchboard  panel  to  which  the  cir- 
cuits of  the  rheostat  are  connected. 

Rhumbs  of  Compass. — The  points  of  the  compass. 

Ribbon  Conductor. — A  conductor  resembling  a  ribbon 
in  shape. 

Ribbon  Copper. — A  copper  conductor  resembling  a  rib- 
bon in  shape. 

Right-^Handed  Armature  Winding. — A  dextrorsal  wind- 
ing of  an  armature  core. 

Right-Handed  Dynamo. — A  dynamo  which  rotates 
right-handedly  when  observed  from  the  pulley  end. 

Right-Handed  Helix. — A  helix  on  which  the  convolu- 
tions of  wire  are  wound  in  a  right-handed  direc- 
tion— in  a  clock-wise  direction. 

Right-Handed  Motor.— A  motor  designed  to  run  in  a 
direction,  when  viewed  from  the  pulley  end,  corre- 
sponding to  the  direction  followed  by  the  hands  of 
a  clock. 

Right-Handed  Solenoid. — A  right-handedly  wound 
solenoid. 

Ring  Armature. — An  armature  whose  core  is  ring- 
shaped. 

Ring  Clutch. — A  clutch,  ring-shaped,  and  serving  to 
clutch  the  lamp-rod  of  an  arc  lamp  when  the  ring 
gets  out  of  horizontal  position. 

Ring  Clutch  for  Arc  Lamp. — A  clutch  resembling  a  ring 
in  shape,  and  which  encircles  the  lamp  rod,  holding 


218  ELECTRICAL  DICTIONARY 

it  firmly  when  in  an  inclined  position,  but  allowing 
it  to  drop  when  in  a  horizontal  position. 

Ring-Connected  Generator. — A  generator  whose  arma- 
ture is  wound  in  such  a  manner  as  to  provide  for 
the  connection  of  corresponding  points  to  ring  con- 
ductors, thereby  equalizing  the  current  distribu- 
tion and  flux  around  the  armature. 

Ring-Magnet. — A  bar  evenly  magnetized  and  made  into 
a  ring. 

Ring-Off. — A  term  applied  to  the  signal  given  by  a  sub- 
scriber when  he  has  finished  using  the  telephone. 

Risers. — "Wires  which  run  vertically  from  floor  to  floor 
in  a  building  in  order  to  furnish  the  different  floors 
with  current  from  the  service  wires. 

River  Cable. — A  sub-aqueous  cable  adapted  for  use  in 
•rivers. 

Riveted  Railway- Joint. — A  rail-joint  effected  between 
two  rails  by  means  of  heavy  fish  plates,  riveted  to 
the  end  of  each  rail. 

Roaring  of  Arc. — A  roaring  noise  accompanying  the 
formation  of  a  strong  voltaic  arc  and  due  to  too 
close  proximity  of  carbons. 

Rocker  Arms. — Arms  projecting  from  a  rocker  and 
each  one  carrying  one  of  the  brush  holders. 

Rocker-Arm  Circle. — The  movable  piece  mounted  con- 
centrically with  the  commutator  and  carrying  the 
rocker  arms  and  brush  holders,  and  which,  by 
being  moved,  adjusts  the  brushes  for  proper  lead. 

Rod-Clamp. — A  clamp  used  in  the  lamp  rod  of  an  arc 
lamp. 

Rod  Clutch. — A  device  serving  to  clutch  the  carbon 
rod  in  an  arc  lamp. 


ELECTRICAL.  DICTIONARY  219 

Roentgen  Effects. — Effects  obtained  by  means  of  the 
Roentgen  or  X-rays. 

Roentgen  Radiograph. — A  term  proposed  for  radio- 
graph. 

Roentgen-Ray  Screen. — A  screen  whose  surface  is  cov- 
ered with  fluorescent  material  for  the  purpose  of 
receiving  and  displaying  a  Roentgen  image. 

Roentgen-Ray  Transformer. — A  transformer  of  alter- 
nating current  and  adaptable  for  operating  a 
Roentgen-ray  tube. 

Roentgen-Ray  Tube. — A  glass  vessel  containing  a  high 
vacuum  and  sealed  hermetically  with  electrodes 
passing  through  it. 

Roentgen  Rays. — A  peculiar  form  of  radiation  discov- 
ered by  Roentgen,  and  which  is  emitted  from  that 
portion  of  a  high  vacuum  tube  upon  which  the 
cathode  rays  fall. 

Roget's  Spiral. — A  cylindrical  helix  of  wire  suspended 
by  one  end,  the  other  end  dipping  into  a  mercury 
cup,  an  active  circuit  being  connected,  one  termi- 
nal to  the  upper  end,  the  other  to  the  mercury  cup, 
thus  bringing  the  apparatus  in- series  into  the  cir- 
cuit, while  the  current  as  it  flows  causes  the  coil 
to  shorten,  each  spiral  attracting  its  neighbor ;  thus 
breaking  the  circuit  by  the  lower  end  being  drawn 
out  of  the  mercury  cup;  and  when  the  current  is 
cut  off  the  coils  do  not  attract  each  other,  and  the 
ends  drop  into  the  mercury  cup  again,  and  in  this 
way  the  circuit  is  alternately  opened  and  closed. 
An  automatic  contact  breaker. 

Rosette. — An  ornamental  device  placed  in  a  wall  or 
ceiling  and  equipped  with  service  wires  in  order 


220  ELECTRICAL  DICTIONARY 

that  an  electric  lamp  or  an  electrolier  may  be  easily 
attached. 

Rosette  Cut-Out. — A  rosette  having  a  cut-out. 

Rotary  Converter. — A  motor  and  dynamo  combined 
whose  function  is  to  transform  a  current  of  any 
kind — high  or  low  voltage,  alternating  or  con- 
tinuous— into  any  other  kind  of  current  desired ; 
the  watts  taken  in  being  in  excess  of  those  put  out. 

Rotary  Current. — A  term  used  signifying  polyphase 
currents  which  can  produce  a  rotary  field. 

Rotary-Field  Induction  Motor. — An  induction  motor 
which  is  operated  by  causing  the  field  coils  to  be 
excited  one  after  another  successively  around  the 
periphery  of  the  armature. 

Rotary-Magnetic  Field. — A  field  resulting  from  a  rotary 
current ;  a  magnetic  field. 

Rotary  Magnetism. — Magnetism  which  a  rotary  mag- 
netic field  produces. 

Rotating  Brushes  of  Dynamo.— Discs  of  metal  which 
rotate  around  the  periphery  of  a  commutator  there- 
by translating  the  current,  and  used  sometimes  in- 
stead of  the  ordinary  brushes. 

Rotating  Current. — A  term  signifying  the  current 
which  is  the  product  of  a  combination  of  alternat- 
ing currents,  the  phases  of  which  are  definitely  dis- 
placed as  referred  to  one  another;  a  multiphase 
current. 

Rotating-Current  Transformer. — Rotary-current  trans- 
former. 

Rotor. — The  rotating  part  of  an  induction  alternating 
electric  machine. 

Rubber  Tape. — A  rubber  insulating  adhesive  tape. 


ELECTRICAL  DICTIONARY  221 

Ruhmkorff  Coil. — A  common  induction  coil  with  circuit 
breaker,  used  with  constant  and  direct  current.  A 
coil  in  which  a  high  voltage  is  induced  in  the  sec- 
ondary coil.  A  step  up  transformer  with  a  circuit 
breaking  attachment. 

Bumble. — A  hollow  cylinder  into  which  are  placed 
small  articles  that  are  to  be  polished  preparatory 
to  electro-plating,  the  cylinder  being  rotated  by 
mechanical  power,  the  articles  are  kept  in  constant 
motion,  and  the  desired  effect  is  obtained  by  their 
attrition  against  one  another  or  against  other  hard 
objects  which  may  be  contained  in  the  cylinder  for 
that  purpose. 

Running  Position  of  Street-Car  Controller. — The  posi- 
tion of  the  switch  handle  while  the  current  which 
keeps  the  motors  in  rotation  is  being  supplied,  and 
a  position  differing  from  that  maintained  while  the 
current  is  cut  off. 

Running  Torque  of  Motor. — The  torque  which  a  motor 
exerts  while  running,  and  to  be  distinguished  from 
the  starting  torque. 


S. 

S.  P.  Cut-Out. — An  abbreviation  meaning  single  pole 

cut-out. 
Safe  Carrying  Capacity  of  a  Conductor. — The  strength 

of  current  which  a  conductor  will  carry  without 

overheating. 

Safety-Catch.— Safety  fuse. 
Safety-Catch  Holder. — Safety  fuse  holder. 
Safety  Device  for  Arc  Lamps  or  Series  Circuit. — An 


222  ELECTRICAL  DICTIONARY 

automatic  device  by  the  operation  of  which  a  path 
for  a  current  around  a  lamp  or  other  defective  de- 
vice in  a  series  circuit  is  made,  thereby  obviating 
the  opening  of  a  whole  circuit. 

Safety  Fuse. — A  wire  or  any  other  suitable  form  of 
metal  which  is  easily  fusible  and  capable  of  carry- 
ing an  ordinary  current  without  fusing,  but  which 
will  fuse  under  an  unusually  strong  current  and 
automatically  break  the  circuit. 

Safety  Fuse-Block. — A  block  serving  to  receive  a  safety 
iuse. 

Sag  of  Conductor  or  Line  Wire. — The  sag  of  an  over- 
head wire  or  conductor  suspended  between  two 
points  of  support. 

Salimeter. — A  hydrometer  by  means  of  which  the  den- 
sity of  saline  solutions  is  measured. 

Saline  Creeping. — A  deposit  of  salts  on  the  walls  of 
solids  immersed  in  saline  solutions,  effected  by 
efflorescence. 

Saline  Solution. — A  salt  dissolved  in  a  liquid. 

Sand-Box  for  Electric  Car. — A  box  containing  sand  and 
attached  to  a  car  for  the  purpose  of  sprinkling  the 
sand  over  the  track,  thereby  increasing  the  friction 
between  the  wheels  and  the  rails. 

Saturated  Solution. — A  solution  which  has  dissolved  as 
much  of  a  solid  as  it  is  capable  of  dissolving  at  a 
given  temperature. 

Sayers  Armature  Winding. — An  armature  winding  de- 
signed to  obtain  sparkless  commutation  by  means 
of  additional  coils,  termed  commutator  coils,  which 
are  exposed  to  the  action  of  an  auxiliary  pole  and 
introduced  into  the  main  circuit. 


ELECTRICAL  DICTIONARY  223 

Scale  Zero. — An  instrument  zero. 

Scarf  Joint  of  Conductors. — A  joint  effected  between 
the  ends  of  conductors  by  cutting  the  ends  on  a 
bias  and  then  soldering  them  together,  thereby 
preserving  a  cylindrical  shape  and  smooth  surface. 

Sciagraph. — A  name  proposed  for  radiograph. 

Scintillating  Jar. — A  Leyden  jar  the  coatings  of  which 
are  made  by  placing  small  pieces  of  tin-foil  on  the 
glass  at  certain  distances  apart,  leaving  small 
spaces  between  them. 

Scratch  Brush. — A  brush  of  wires  or  stiff  bristles  serv- 
ing to  remove  all  foreign  matter  from  the  surface 
of  metallic  articles  preparatory  to  electro-plating. 

Screen,  Electric. — A  cage,  plate  or  hollow  case  com- 
posed of  a  conducting  substance  and  having  an 
earth  connection  so  as  to  protect  from  electrostatic 
influences  any  object  placed  inside  of  it. 

Screening  Effect  of  Eddy  Currents. — The  effect  which 
eddy  currents  cause  in  a  solid  body  of  iron  or  steel, 
and  which  consists  in  protecting  the  interior  of  the 
body  from  the  influence  of  an  external  alternating 
magnetic  field. 

Sea  Cell  Test. — A  circuit  test  used  in  submarine  electric 
torpedo  work  and  accomplished  by  means  of  a 
single  voltaic  cell,  the  sea  water  serving  as  the  elec- 
trolyte. 

Seal  of  Meter  — A  seal  of  lead  put  on  a  meter  to  guard 
against  tampering  with  the  meter  after  it  has  been 
set. 

Sealing-In  of  Filament. — The  hermetical  sealing  of  an 
incandescent  lamp  between  the  support  of  the  fila- 
ment and  the  lamp  chamber. 


224  ELECTRICAL  DICTIONARY 

Sealing-Off  of  Lamp  Chamber. — The  hermetical  sealing 
of  a  lamp  chamber  by  fusing  the  glass  w^iile  the 
lamp  is  still  connected  with  the  pumps. 

Search-light,  Electric. — An  apparatus  which  produces 
a  powerful  stream  of  light  and  projects  it  in  any 
direction,  employing  a  focusing  -arc  lamp,  which, 
provided  with  large  carbons,  is  enabled  to  use  a 
heavy  current;  and  the  lamp  is  so  situated  as  to 
project  the  greater  part  of  the  light  onto  a  suitable 
reflector  or  lens,  thereby  concentrating  the  rays 
into  one  immense  beam. 

Secondary. — A  term  applied  to  the  secondary  coil  of  a 
transformer  or  induction  coil. 

Secondary  Ampere  Turns. — The  ampere  turns  in  the 
secondary  coil  of  an  induction  coil  or  transformer. 

Secondary  Battery! — A  storage  battery. 

Secondary  Cell. — A  storage  cell. 

Secondary  Clock. — A  clock  in  a  system  of  time  teleg- 
raphy, whose  movements  are  controlled  by  the  cur- 
rent, regulated  by  the  master  clock. 

Secondary  Coil  of  Transformer. — A  transformer's  coil 
which  receives  energy  from  the  primary  coil.  The 
secondary  winding  of  an  induction  coil  or  trans- 
former. 

Secondary  Currents. — Currents  produced  in  a  conduc- 
tor by  changes  in  currents  in  a  contiguous  conduc- 
tor. The  currents  produced  in  the  secondary  cir- 
cuit of  an  induction  coil  or  alternating  current 
converter. 

Secondary  Fuse-Box. — A  fuse-box  placed  in  a  transfor- 
mer's secondary  circuit  or  in  that  of  an  induction 
coil. 


ELECTRICAL  DICTIONARY  225 

Secondary  Plate  of  Condenser. — The  plate  of  a  con- 
denser which  becomes  charged  by  reason  of  the  ex- 
istence of  a  charge  in  the  opposite  plate. 

Secret  Telephone  System. — A  telephone  system  ope- 
rated independent  of  an  exchange  or  an  attendant 
and  arranged  in  such  a  manner  as  to  enable  per- 
sons to  communicate  with  each  other  between  any 
two  stations  without  being  heard  by  any  other  per- 
son on  the  line. 

Section. — The  intersection  of  two  superficies,  or  of  a 
superficies  and  a  solid;  in  the  former  case  a  line, 
in  the  latter  a  surface.  A  length  of  conductor  in- 
sulated from  contiguous  portions,  as  observable  in 
trolley  systems. 

Section  Circuit-Breaker. — A  magnetic  circuit-breaker 
by  which  a  trolley  wire  section  is  controlled. 

See-Sawing. — A  term  which  describes  the  improper 
synchronization  of  two  parallel  connected  alter- 
nators. 

See-Sawing  of  Parallel  Connected  Generator. — Im- 
proper synchronization  existing  between  gene- 
rators. 

Segment  Switch. — A  switch  in  which  an  arm  is  pivoted 
in  such  a  manner  as  to  enable  it  to  describe  in  its 
movement  the  arc  of  a  circle,  which  is  divided  into 
insulated  segments. 

Selectance. — A  quality  possessed  by  resonant  electric 
circuits  and  by  virtue  of  which  they  respond  to 
one  frequency  of  alternating  current  more  than  to 
another. 

Selective  Absorption. — A  selected  character  of  absorp- 
tion of  the  waves  of  light,  heat,  electricity  or 
sound. 


226  ELECTRICAL  DICTIONARY 

Selective  Consonance. — A  quality  possessed  by  a  con- 
sonant alternating  current  circuit  by  virtue  of 
which  it  responds  to  one  frequency  more  than  to 
another. 

Selective  Resonance. — That  quality  possessed  by  a  reso- 
nant circuit  and  by  virtue  of  which  it  becomes 
selective  to  a  definite  frequency  of  alternating  cur- 
rent. 

Selective-Signal  Pendulum. — A  system  of  selective  sig- 
naling wherein  the  receiving  bells  are  each  actu- 
ated by  a  single  alternating  current  frequency,  and 
the  transmitting  frequency  is  adjusted  to  agree  by 
changing  the  length  of  a  pendulum  in  the  trans- 
mitter. 

Selective  Signaling  Apparatus. — Individual  signaling 
apparatus. 

Selenium. — An  elementary  substance  allied  to  sulphur, 
its  resistance  being  very  susceptible  to  the  action 
of  light. 

Selenium  Eye. — A  crude  imitation  of  the  human  eye  in 
which  the  eyelids  are  represented  by  two  slides 
and  selenium  resistance  represents  a  retina. 

Selenium  Photometer. — A  photometer  determining  by 
comparison  the  intensity  of  light;  the  means  of 
comparison  being  the  changes  in  the  resistance  of 
a  selenium  resistance  by  successive  exposures 
under  like  conditions  first  to  the  light  to  be  meas- 
ured, then  to  a  standard  light. 

Selenium  Resistance. — A  resistance  demonstrated  by 
means  of  a  mass  of  selenium  which,  when  exposed 
to  the  light,  experiences  a  variation  of  value  cor- 
responding to  the  variations  in  the  intensity  of 
the  light. 


ELECTRICAL  DICTIONARY  227 

Self -Acting  Make-and-Break. — An  automatic  make-and- 
break  device. 

Self -Aligning  Bearings. — Bearings  for  journals  which 
are  devised  and  adjusted  in  such  a  manner  as  to 
allow  to  a  small  extent  an  angular  movement, 
which  enables  them  to  conform  to  the  surface  of 
the  shaft. 

Self-Cleaning  Contact  Key. — A  term  applied  to  a  key 
which  has  a  rubbing  contact. 

Self-Contained  Engine  or  Machine. — An  engine  or  ma- 
chine containing  within  itself  all  its  working  parts 
supported  on  a  single  solid  foundation. 

Self -Excitation. — An  excitation  of  a  generator's  field 
magnets  by  the  passage  of  its  own  current  through 
its  own  field  coils. 

Self-Excited. — Excited  by  its  own  current. 

Self-Excited  Alternator. — An  alternator  the  fields  of 
which  are  self-excited. 

Self-Excited  Dynamo. — A  dynamo  the  field  of  which 
is  self-excited. 

Self-Excited  Series-Wound  Continuous-Current  Gen- 
erator.— A  continuous-current  generator  with  a 
series-wound  field,  whose  excitation  is  due  to  the 
current  from  the  generator's  own  armature. 

Self-Excited  Shunt-Wound  Continuous- Current  Gen- 
erator.— A  continuous-current  generator  with  a 
shunt-wound  field,  whose  excitation  is  produced  by 
some  of  the  current  diverted  in  its  passage  from 
the  armature  to  the  external  circuit. 

Self-Induced  Current. — A  current  which  is  induced  in 
a  circuit  by  alterations  in  its  own  strength  attend- 
ing the  opening  or  the  closing  of  a  circuit. 


228  ELECTRICAL  DICTIONARY 

Self-Oiling  Bearings. — Bearings  employing  automatic 
oilers. 

Self -Oiling  Journal. — A  journal  employing  automatic 
oilers. 

Self-Registering  Tachometer. — A  tachometer  whose  in- 
dications of  the  different  speeds  of  a  machine  are 
permanent. 

Self -Regulating  Dynamo. — A  self -regulating  generator. 

Self-Regulating  Generator. — A  generator  which,  by 
reason  of  the  manner  in  which  it  is  wound,  main- 
tains automatically,  notwithstanding  any  change 
in  the  resistance  of  its  load,  either  a  constant-cur- 
rent in  the  circuit  or  a  constant  difference  of  po- 
tential. 

Self-Regulating  X-Ray  Tube.— An  X-ray  tube  which 
is  capable  of  automatically  adjusting  the  degree 
of  vacuum  and  controlling  consequently  the  elec- 
tric pressure  at  the  terminals. 

Self -Starting  Alternating-Current  Motor. — An  alternat- 
ing current-motor  provided  with  the  means  which 
enable  it  to  start  with  any  normal  load. 

Self-Winding  Clock. — A  clock  which  automatically 
winds  itself  by  means  of  a  small  electro-magnetic 
motor  which  obtains  its  current  from  one  or  sev- 
eral voltaic  cells,  the  whole  apparatus  being  in- 
closed within  the  clock's  case. 

Semaphore. — An  apparatus  for  exhibiting  signals  and 
used  in  the  railroad  block  system. 

Semaphore  Arm. — An  arm  of  a  semaphore  capable  of 
being  moved  about  to  exhibit  the  signals  which 
indicate  the  condition  of  the  block  sections  with 
respect  to  trains. 


ELECTRICAL  DICTIONARY  229 

Semi-Circular. — Pertaining  to  a  semi-circle. 

Semi-Period. — A  half  period;  the  time  consumed  by  a 
reversal. 

Sensibility  of  a  Galvanometer. — The  degree  to  which 
the  needle  of  the  galvanometer  is  affected  in  its  de- 
flections by  an  electric  current  passing  through  its 
coils.  The  deflection  which  a  definite  small  current 
strength  causes. 

Sensitive  Telephone. — A  telephone  which  is  capable  of 
performing  its  functions  with  less  current  than 
that  which  is  usually  required  in  telephone  opera- 
tion. 

Sensitive  Tube. — A  coherer. 

Separable  Iron  Core. — An  iron  core  capable  of  being 
separated  from  the  machine  of  which  it  is  an  ac- 
cessory. 

Separate  Circuit  Dynamo. — A  dynamo  which  is  able  to 
furnish  the  current  to  a  number  of  separate  cir- 
cuits. A  form  of  self-exciting  dynamo. 

Separate-Coil  Machine. — A  machine  the  armature  coils 
of  which  are  separated  from  each  other  mechani- 
cally and  not  interlaced  as  in  another  form  of  ma- 
chine. 

Separate  Excitation. — A  dynamo-electric  machine 
whose  field  magnets  are  excited  by  a  separate  .coil 
or  winding  in  the  armature  put  there  for  that  pur- 
pose. 

Separately-Excited  Alternator. — The  excitation  of  the 
field  magnets,  effected  by  external  influence. 

Separately-Excited  Dynamo-Electric  Machine. — A  dy- 
namo-electric machine  the  field  coils  of  which  are 
excited  separately. 


230  ELECTRICAL  DICTIONARY 

Separately-Excited  Field. — The  field  of  a  dynamo  sup- 
plied with  its  magnetizing  current  by  a  source  out- 
side. 

Series    and    Magneto    Dynamo-Electric    Machine. — A 

dynamo  compound  wound,  in  which  the  find  wind- 
ing on  the  field  magnets  is  excited  by  the  armature 
of  a  magneto-electric  machine  with  which  it  is  con- 
nected. 

Series-and-Separately-Excited  Dynamo-Electric  Ma- 
chine.— A  compound-wound  dynamo  which  pro- 
vides for  a  winding  of  its  field  magnet  cores  with 
two  distinct  circuits,  one  core  forming  a  connec- 
tion with  the  field  magnets  and  outside  circuit 
in  series,  while  the  other  forms  a  connection  with 
some  other  source,  which  causes  its  individual  ex- 
citation. 

Series-and-Shunt- Wound-Dynamo-Electric  Machine. — A 

compound-wound  dynamo  whose  winding  of  field 
magnets  consists  of  two  distinct  coils,  one  of  which 
is  wound  with  the  armature  and  outside  circuit, 
in  series,  while  the  other  is  wound  in  shunt  with 
the  armature. 

Series-Arc  Cut-Out. — A  contrivance  by  means  of  which 
a  short  circuit  past  a  defective  lamp  in  a  series-con- 
nected circuit  is  automatically  secured,  which  pro- 
vides for  the  undisturbed  operation  of  all  the  other 
lamps  in  case  of  the  failure  of  any  one. 

Series  Circuit. — A  circuit  established  by  an  arrange- 
ment of  the  separate  sources  and  electro-receptive 
devices,  which  provides  that  the  current  produced 
in  the  circuit  shall  pass  successively  through  the 
entire  circuit. 


ELECTRICAL  DICTIONARY  231 

Series-Connected  Battery. — A  battery  consisting  of 
series-connected  cells. 

Series-Connected  Incandescent  Lamps. — Lamps  which 
are  connected  to  a  circuit  in  series,  a  cut-out  of 
some  description  being  employed,  so  that  in  the 
event  one  lamp  should  be  extinguished  the  others 
would  continue  their  efficient  operation. 

Series-Connected  Electro-Receptive  Devices. — Electro- 
receptive  devices  connected  in  series  to  a  circuit 

Series-Connected  Sources. — Separate  sources,  acting  as 
single  sources,  due  to  the  manner  in  which  they 
are  connected  in  series. 

Series-Connected  Translating  Devices.  —  Series-con- 
nected electro-receptive  devices. 

Series-Connected  Voltaic  Cells. — Voltaic  cells  which 
possess  the  ability  to  act  as  a  single  source  by 
reason  of  the  manner  in  which  they  are  connected 
in  series. 

Series  Connection. — A  number  of  distinct  electric 
sources,  electro-receptive  devices,  or  circuits,  con- 
nected in  such  manner  as  to  obtain  a  passage  of 
the  current  from  first  to  last  in  the  circuit  suc- 
cessively. 

Series  Distribution. — A  distribution  of  electricity  in 
which  the  receptive  devices  are  arranged  in  suc- 
cessive order  upon  one  conductor  extending  the 
entire  length  of  the  circuit. 

Series  Dynamo. — A  series-wound  dynamo. 

Series  Field-Terminals  of  Motor. — Terminals  of  a  com- 
pound-wound motor  with  which  the  ends  of  a  se- 
ries field  winding  are  connected. 


232  ELECTRICAL,  DICTIONARY 

Series  Incandescent  Lamp.— An  incandescent  lamp 
adaptable  for  service  in  a  series  circuit. 

Series  Incandescent  Lighting  System. — A  system  of  in- 
candescent lighting  differing  from  the  multiple  sys- 
tem in  the  manner  of  connecting;  the  former  sys- 
tem having  its  lamps  connected  in  series,  while  in 
the  latter  they  are  connected  in  parallel. 

Series  Motor. — A  motor  adaptable  for  use  in  a  series 
circuit.  A  motor  whose  field  coil  winding  is  in  se- 
ries with  the  armature. 

Series-Multiple. — A  series-multiple  connection. 

Series-Multiple-Controller. — A  controller  designed  for 
a  double  motor  car  and  which  operates  by  connect- 
ing the  motors  either  in  series  or  in  parallel,  with  or 
without  resistance,  its  function  being  to  stop,  start, 
vary  the  speed  of  the  car  or  vary  the  torque  of 
the  motors. 

Series-Multiple  Circuit. — A  compound  circuit  where  a 
number  of  separate  groups  composed  of  distinct 
sources  or  electro  devices,  or  both,  connected  in 
groups  in  multiple  arc,  are  afterwards  connected 
in  series. 

Series-Multiple-Connected  Sources. — A  single  source 
formed  by  the  connection  of  a  number  of  distinct 
electric  sources,  and  in  this  single  source  the  dis- 
tinct sources  are  connected  in  a  number  of  dis- 
tinct multiple  circuits,  and  these  circuits  are  con- 
nected together  in  series  separately. 

Series-Parallel  Controller. — A  series  multiple  controller. 

Series-Winding. — A  method  of  winding  a  generator  or 
motor,  in  which  one  of  the  commutator-brush  con- 
nections is  connected  to  the  field  magnet  winding, 
the  other  end  of  the  magnet  winding  being  con- 


ELECTRICAL  DICTIONARY  233 

nected  with  the  outer  circuit,  and  the  other  arma- 
ture brush  being  connected  with  the  other  terminal 
of  the  outer  circuit. 

Service  Block. — A  block  serving  to  support  and  con* 
nect  service  wires. 

Service  Wires. — Wires  connected  to  the  supply  circuit 
or  main  and  which  run  into  a  building  or  structure 
to  supply  the  current. 

Sextipolar. — Having  six  poles. 

Sextipolar  Dynamo.— A  dynamo  with  a  sextipolar  field. 

Sextipolar  Field* — A  field  created  by  six  magnet  poles. 

Shadow  Photometer. — A  photometer  in  which  the  rela- 
tive intensity  of  the  two  lights  is  estimated  by  the 
intensity  or  strength  of  the  shadows  of  the  same 
object  which  they  respectively  cast. 

Shear. — A  stress  consisting  of  a  lateral  projection  com- 
bined with  an  equal  perpendicular  compression. 

Shearing  Stress. — A  stress  causing  a  shear. 

Sheathing  a  Cable. — The  covering  which  is  used  to  pro- 
tect a  cable. 

Sheathing  Wires. — The  wires  which  are  used  for  the 
armor  of  a  submarine  cable. 

Shell  of  Commutator. — A  commutator  core  apart  from 
the  shaft. 

Shell  Transformer. — A  transformer  having  its  primary 
and  secondary  coils  placed  one  upon  the  other,  and 
they  are  entirely  inclosed  by  the  iron  core  which 
is  wound  through  and  over  them. 

Shellac. — A  vegetable  substance  of  a  resinous  nature 
obtained  from  the  juices  of  certain  tropical  plants 
and  valuable  for  its  superior  insulating  qualities 
and  inductive  capacity. 


234  ELECTRICAL  DICTIONARY 

Shifting  Magnetic  Field. — A  magnetic  field  which  ro- 
tates, its  lines  of  magnetic  force  varying  in  posi- 
tion as  referred  to  the  magnet  pole  which  emits 
them. 

Shifting  Zero. — A  zero  which  changes  its  position. 

Ship  Dynamometer. — A  dynamometer  which  serves  to 
indicate  the  strain  on  a  grappling  cable  and  used 
on  cable  ships. 

Shock. — A  sudden  striking  agaftist ;  a  collision ;  a  sharp 
concussion  of  one  thing  against  another;  the  vio- 
lent agitation  of  the  nervous  system. 

Shock,  Electric. — -The  sudden  convulsion  of  the  mus- 
cles, with  a  feeling  of  pain,  occasioned  by  an  elec- 
tric discharge  through  the  animal  system. 

Shoe  of  Contact  for  Street  Railway. — A  metallic  cast- 
ing employed  on  street  railroads  in  connection  with 
a  rail-brake  and  serving  to  stop  the  car  by  the  re- 
sistance offered,  due  to  its  friction  upon  the  rail. 

Short  Arc  System  of  Electric  Lighting. — A  system  of 
lighting  effected  by  short  voltaic  arcs  between  car- 
bon electrodes. 

Short  Circuit. — A  connection  between  two  parts  of  a 
circuit,  which  connection  is  a  low  resistance  com- 
pared to  the  intercepted  portion;  a  shunt  or  by- 
path. A  term  used  also  as  a  verb,  as  "to  short 
circuit  a  lamp";  "to  cut  out  of  circuit  by  a  short 
conductor. ' ' 

Short-Circuited  Conductor.— A  conductor  having  a 
short  circuit  connected  past  it. 

Short-Circuiting  a  Dynamo-Electric  Machine. — Employ- 
ing a  short  circuit  to  cut  out  the  outer  circuit  of 
a  dynamo.  Connecting  the  poles  of  a  dynamo  by 
a  circuit  of  low  resistance. 


ELECTRICAL  DICTIONARY  235 

Short-Sightedness. — A  defect  in  the  eye  which  causes 
objects  to  appear  indistinct  when  not  near  to  the 
eye,  and  which  is  caused  by  abnormal  convexity 
of  the  eyeball. 

Shunt. — A  connection  in  parallel  with  a  portion  of  the 
circuit  in  a  current  circuit. 

Shunt. — To  establish  a  connection  in  parallel  with  a 
portion  of  the  circuit. 

Shunt-Breaking  Resistance. — A  resistance  employed  in 
a  field  of  a  shunt  dynamo,  so  that  when  breaking 
its  circuit  the  danger  of  producing  excessive  in- 
duced pressure  may  be  obviated. 

Shunt- Circuit. — A  subsidiary  circuit  in  any  part  of  a 
circuit  where  the  current  divides,  some  of  it  flow- 
ing in  the  main  circuit  and  some  of  it  through  the 
subsidiary  or  shunt.  A  partial  circuit  connected 
to  two  points  of  another  circuit  and  running  par- 
allel with  it  between  the  two  points. 

Shunt-Coil. — A  coil  in  a  shunt  circuit. 

Shunt  Dynamo. — A  shunt-wound  dynamo. 

Shunt-Field  Terminals  of  Motor. — The  terminals  of  an 
electric  motor's  shunt-field  coils. 

Shunt  for  Ammeter. — A  shunt  coil  serving  to  change 
the  value  of  the  readings  of  an  ammeter  and  which 
is  connected  in  multiple  with  the  coils  thereof. 

Shunt-Rheostat. — A  rheostat  in  a  shunt-circuit. 

Shunt  Turns  of  Dynamo. — In  a  shunt-wound  or  com- 
pound-wound dynamo  shunt  turns  signify  the  am- 
pere turns. 

Shunt-Winding. — The  winding  of  a  dynamo  in  which 
the  field  magnet  winding  is  in  shunt  or  parallel 
with  the  winding  of  the  armature. 


236  ELECTRICAL  DICTIONARY 

Shunt-Wound  Dynamo-Electric  Machine. — A  dynamo 
electric  machine  whose  commutator  brushes  have 
two  connections,  one  set  being  the  terminals  of  the 
outer  circuit,  while  the  other  set  are  the  terminals 
of  the  field  magnet  windings;  or,  in  other  terms, 
the  field  magnet  windings  are  in  shunt  or  in  par- 
allel with  the  outer  circuit. 

Shunt-Wound  Motor. — A  motor  the  field  magnet  coils 
of  which  are  connected  in  shunt  to  the  armature 
circuit. 

Shunted. — Having  a  shunt. 

Shuttle  Armature. — The  original  Siemans'  armature, 
now  in  disuse.  A  form  of  drum  armature  having 
a  long,  narrow  core  and  its  cross  section  cor- 
responding nearly  to  the  form  of  an  H,  the  grooves 
of  which  are  wound  full  of  wire,  so  that  the  whole 
forms  almost  a  perfect  cylinder. 

Side-Bar  Suspension  of  Motor. — The  employment  of  two 
light  rods  mounted  on  springs,  which  are  parallel 
to  the  side  frames,  for  the  purpose  of  supporting 
the  motors  in  a  street  railway  car  truck. 

Side  Commutator. — The  commutator  of  a  dynamo-elec- 
tric machine  which  is  set  on  the  side  of  the  revolv- 
ing armature. 

Side  of  Three- Wire  System. — In  the  three-wire  system 
of  distribution  a  term  used  signifying  the  positive 
or  negative  conductor. 

Side  Suspension  of  Motor. — The  suspension  of  motor 
by  means  of  side  bars. 

Sides  of  Three-Wire  System. — Those  parts  of  the  three- 
wire  system  having  positive  and  negative  poten- 
tials respectively. 


ELECTRICAL  DICTIONARY  237 

Siemens  Electro-Pyrometer. — An  instrument  for  the 
determination  of  temperatures  by  the  variations  in 
electric  resistance  in  a  platinum  wire  exposed  to 
the  heat  which  is  to  be  measured. 

Signal-Service  System  for  Electric  Railroads. — A  sys- 
tem of  electric  signals  in  use  on  railroads  for  ob- 
taining information  pertaining  to  the  operation  of 
the  road,  the  giving  of  instructions  to  trainmen  and 
others  and  for  general  communication  from  sta- 
tions to  trains. 

Sight  Feeding  Oiler. — An  oil  cup  made  of  glass,  by 
means  of  which  the  feeding  of  oil  can  be  observed. 

Silver  Bath. — A  solution  of  a  salt  of  silver  for  deposi- 
tion in  the  electro-plating  process.  An  electrolytic 
bath  containing  a  solution  of  a  salt  of  silver,  with 
a  plate  of  silver  immersed  in  it  and  serving  as  the 
anode;  the  article  to  be  plated  serving  as  the 
cathode. 

Silver-Palladium  Alloy. — An  alloy  of  silver  palladium 
and  other  metals,  valuable  for  its  non-magnetic 
properties  and  much  used  for  certain  parts  in  the 
works  of  watches. 

Silver-Plating. — Depositing  a  coat  of  silver  upon  the 
surfaces  of  base  metals  by  the  process  of  electro- 
plating. 

Simple  Arc. — A  voltaic  arc  produced  between  only  two 
electrodes. 

Simple  Circuit. — A  circuit  having  a  single  generator 
and  a  single  receiver,  such,  for  instance,  as  a  motor 
or  sounder  with  a  single  connecting  conductor. 

Simple-Harmonic  Currents. — Currents  with  a  variable 
flow  in  strength  and  duration;  a  simple  harmonic 
curve  serving  to  represent  the  quantity  of  elec- 


238  ELECTRICAL  DICTIONARY 

tricity  passing  by  any  section  of  conductor.  Such 
a  character  of  current  that  a  simple  harmonic  curve 
may  express  the  continuous  variation  of  the  flow 
past  any  area  of  cross-section  of  the  conductor,  or 
the  continuous  variations  in  electro-motive  force. 

Simple-Harmonic  Curve. — The  curve  which  results 
when  a  simple-harmonic  motion  in  one  line  is  com- 
pounded with  uniform  motion  in  a  straight  line  at 
right  angles  thereto. 

Simple-Harmonic  Motion. — Motion  of  a  point  back  and 
forth  along  a  line;  the  motion  of  a  pendulum,  as 
regards  its  successive  swings  back  and  forth,  is 
an  example  of  harmonic  motion.  Simple-periodic 
motion. 

Simple  Immersion. — -Electro-plating  without  a  battery 
and  by  simply  immersing  the  metal  in  a  solution 
of  metallic  salt. 

Simple  Magnet. — A  magnet  made  of  one  piece  of  metal. 

Simple  Shunt. — A  coil  designed  as  a  shunt;  having  no 
iron  core. 

Simplex  Telegraphy. — -A  system  of  telegraphy  provid- 
ing for  the  transmission  of  a  single  message  only 
over  the  line  wire. 

Sine  Galvanometer. — A  galvanometer  whose  measure- 
ments are  contingent  upon  the  sine  of  the  angle 
of  deflection  produced  when  the  coil  and  needle 
rest  in  the  one  vertical  plane. 

Single  Brush-Rocker  Arm.- — An  arm  holding  a  single 
pair  of  brushes  in  such  a  position  on  a  dynamo  or 
motor  as  to  enable  them  to  be  shifted  easily  into 
the  required  position  on  the  commutator. 

Single-Contact  Carbon  Telephone. — A  style  of  telephone 
transmitter  with  a  single  contact. 


ELECTRICAL,  DICTIONARY  239 

Single-Coil  Field  Dynamo. — A  dynamo  with  a  magnetic 
field  which,  is  produced  by  a  single  magnetizing 
coil. 

Single  Field-Coil  Multipolar  Dynamo. — A  multipolar 
dynamo  provided  with  a  single  field-coil  on  a  single 
core,  and  having  a  number  of  polar  projections. 

Single-Fluid  Hypothesis  of  Electricity. — A  hypothesis 
which  attributes  electrical  phenomena  to  the  pres- 
ence or  absence  of  a  single  fluid. 

Single-Loop  Armature. — An  armature  provided  with  a 
closed  conducting  circuit,  with  a  single  loop,  and 
situated  in  such  a  manner  as  to  enable  it  to  revolve 
in  a  magnetic  field  and  cut  its  magnetic  flux. 

Single-Magnet  Dynamo-Electric  Machine. — A  single 
field-coil  dynamo. 

Single-Pair  Brush  Yoke. — A  device  for  holding  a  single 
pair  of  brushes  on  a  dynamo  so  as  to  enable  them 
to  be  shifted  easily  in  the  required  position  on  the 
commutator. 

Single  Phase. — A  phase  characterizing  that  which  is 
present  in  ordinary  alternating  currents  in  a  simple 
alternating  current  system;  being  uniphase  or 
monophase  differs  in  this  respect  from  multiphase 

currents. 

Single-Phase  Motor. — A  monophase  motor. 

Single-Phase  Induction  Motor. — An  induction  motor 
which  is  designed  to  operate  on  a  uniphase  alter- 
nating current  circuit. 

Single  Phase  Synchronous  Motor. — A  synchronous 
motor  which  can  be  operated  by  monophase 
currents. 


240  ELECTRICAL  DICTIONARY 

Single-Phase  Transformer. — A  transformer  designed 
to  supply  or  transform  uniphase  currents. 

Single-Pole  Cut-Out. — A  cut-out  which  breaks  the  cir- 
cuit or  cuts  in  only  one  lead. 

Single-Pole  Switch. — A  switch  employed  to  open  or 
close  at  only  one  lead. 

Single-Pole  Telephone  Receiver. — A  telephone  receiver 
having  but  one  pole  presented  to  the  diaphragm, 
and  in  this  respect  differing  from  a  receiver  where- 
in two  poles,  each  inclosed  within  a  coil,  are  pre- 
sented to  the  diaphragm. 

Single-Reduction. — Speed-reducing  by  a  single  gear 
wheel  only.  A  gearing  through  the  medium  of 
which  a  single  reduction  of  speed  is  effected  as  dis- 
tinguished from  a  double  gearing  in  which  two 
separate  reductions  are  effected. 

Single-Reduction  Street-Car  Motor. — A  street-car  motor 
whose  car-axle  motion  is  reduced  by  means  of  a 
single  reduction  gear,  connected  with  the  car  axle, 
as  distinguished  from  a  motor  which  is  geared, 
through  two  successive  gear  wheels,  with  the  car 
axle. 

Single-Stroke   Electric   Bell. — An   electric   bell   which 

only  strikes  once  each  time  the  circuit  is  closed. 
Single-Throw  Switch. — A  switch  which,  in  opening  and 

closing  a  circuit,  assumes  two  positions  only. 
Single-Trolley   System. — A   trolley   system    employing 

only  one  overhead  conducting  wire,  .the  track  and 

ground  serving  as  a  return. 
Single-Truck  Car. — A  car  whose  body  is  borne  on  a 

single  truck. 
Single-Wire     Multiple     Telephone     Switchboard. — A 


ELECTRICAL  DICTIONARY  241 

switchboard  having  the  jacks  all  in  series  in  each 
line  and  serving  to  connect  ground-return  sub- 
scribers' lines.  A  single-cord  multiple  switch- 
board employed  in  telephone  service. 
Single-Wound  Gramme  Ring. — A  gramme  ring  having 
a  single  winding,  in  which  the  number  of  coils 
is  a.  multiple  of  the  number  of  poles,  and  the  num- 
ber of  commutator  segments  equals  the  number  of 
poles. 

Single-Wound  Multiple-Circuit  Multipolar  Drum-Arma- 
ture.— A  drum-armature  so  wound  as  to  obtain  a 
multipolar  field  in  a  single  winding  and  afford  a 
number  of  paths  between  the  brushes. 

Single- Wound  Two- Circuit  Drum- Armature, — A  drum- 
armature  wound  for  a  multipolar  field,  with  a  sin- 
gle winding,  and  which  provides  for  two  circuits  or 
paths  between  the  circuit. 

Single-Wound  Two-Circuit  Multipolai  ftijig- Armature. 
— A  ring  armature  so  wound  £s  6C  obtain  a  multi- 
polar  field,  with  a  single  wind  ;ag,  and  which  pro- 
vides for  but  two  circuit?  or  paths  between  the 
brushes. 

Single-Wound  Wire. — Wire  insulated  by  winding,  or 
otherwise,  with  a  single  layer  of  material  only. 

Sinistrorsal  Solenoid. — A  left-handed  solenoid. 

Sinusoid, — A  curve  of  sines. 

Sinusoidal  Alternating  Electromotive  Force. — Alter- 
nating electromotive  forces  represented  as  to  vari- 
ations in  strength,  by  a  sinusoidal  curve. 

Sinusoidal  Currents. — Simple  periodic  currents  the 
strengths  of  which  are  represented  accurately  by 
sinusoids. 


242  ELECTRICAL  DICTIONARY 

Siphon  Electric — A  siphon  which  provides  by  electrical 
means  for  the  continuation  of  the  flow  of  liquid, 
which  has  ceased  to  flow,  due  to  the  accumulation 
of  air. 

Siphon  Recorder. — A  recording  apparatus  in  which  the 
inked  marks  are  made  on  a  strip  of  paper,  the  ink 
being  supplied  by  a  siphon  terminating  in  a  cap- 
illary orifice. 

Siren. — An  acoustic  instrument  serving  to  measure  the 
frequency  of  sound  waves. 

Six- Wire  System. — A  distributing  system  wherein  five 
dynamos  are  connected  to  six  conductors,  and 
which  partakes  in  general  of  the  character  of  the 
three-wire  system. 

Six-Wire  Triphase  System. — A  system  producing  tri- 
phase  currents,  in  three  distinct  circuits,  having 
two  wires  each. 

Skew  Adjustment  of  Carbons  in  Arc-Lamps — A  manner 
of  adjusting  carbons  in  an  arc  lamp,  the  positive 
carbon  being  placed  a  little  in  front  of  the  negative 
carbon,  but  out  of  vertical  line  with  it. 

Skidding  of  Car  Wheels. — The  sliding  instead  of  the 
rolling  of  the  wheels  of  a  car. 

Skin  Currents. — Rapidly  alternating  currents  which 
are  confined  to  the  superficial  portions  of  a  con- 
ductor. 

Skin  Effect. — A  tendency  of  currents   of  very  brief 

duration  to  flow  through  the  outer  layers  and  to 

avoid  the  mass  df  a  solid  conductor. 
Sled. — In  a  conduit  system,  a  contact  for  an  electric 

car  like  the  plow,  except  that  it  is  drawn  after  the 

car  instead  of  being  pushed  ahead. 


ELECTRICAL  DICTIONARY  243 

Sleeve  Joint. — A  joint  obtained  by  inserting  the  ends  of 
the  wires  or  electric  conductors  into  a  metallic  tube 
or  sleeve  of  sufficient  inside  diameter  to  just  admit 
them,  and  then  securing  them  by  twisting  and 
soldering. 

Slide  Bridge. — A  style  of  Wheatstone  's  bridge,  a  single 
thin  wire  representing  one  lateral  pair  of  arms, 
the  other  pair  representing  a  resistance  which  is 
known  and  the  one  to  be  ascertained ;  and  between 
the  known  and  the  unknown  resistance  the  gal- 
vanometer is  connected  on  one  side,  its  connection 
on  the  opposite  side  being  moved  back  and  forth 
until  the  balance  is  obtained  and  the  galvanometer 
strikes  zero. 

Slide  Resistance. — A  rheostat  the  placing  and  remov- 
ing of  whose  separate  resistances  of  coils  from  a 
circuit  are  effected  by  means  of  a  sliding  contact. 
An  instrument  used  in  telegraphy  and  formed  of 
two  slide  rheostats  divided  into  100  parts  each,  but 
constituting  both  together  a  rheostat  in  effect,  sub- 
divided into  10,000  parts. 

Sliding  Bed-Plate. — A  bed-piece  or  plate  of  a  belt- 
driven  dynamo  which  is  capable  of  being  moved 
for  the  purpose  of  tightening  the  belt. 

Sliding  Contact. — A  contact  which  is  connected  with 
one  part  of  a  circuit  and  closes  that  circuit  by  being 
slid  over  a  conductor  connected  with  another  part 
of  the  circuit. 

Slings. — Polished  copper  wires  used  in  electro-plating, 
by  which  the  article  to  be  plated  is  suspended  from 
the  negative  rod  in  the  depositing  tank. 

Slip  of  Induction  Motor. — The  ratio  of  difference  be- 
tween the  speed  of  the  rotary  magnetic  field  by 


244  ELECTRICAL  DICTIONARY 

which  the  motor  is  driven  and  the  speed  of  the 
rotor. 

Slip  of  Rotor. — The  ratio  of  difference  between  the 
speed  of  a  rotary  magnetic  field  and  that  of  the 
rotor. 

Slipping  of  Belt. — The  speed  lost  by  a  revolving  belt 
due  to  its  slipping  on  its  pulley. 

Slots  on  Armature  Core. — The  grooves  in  an  armature 
core  designed  to  receive  the  armature  coils. 

Slot-Wound  Armature. — An  armature  wherein  the 
windings 'are  sunk  in  slots. 

Slotted  Armature. — An  armature  with  grooves  designed 
to  receive  the  wires.  An  iron-clad  armature. 

Slotted  Conduit. — An  underground  conduit  having  a 
slot  which  reaches  to  the  surface  of  the  roadbed, 
by  means  of  which  a  traveling  conductor  is  enabled 
to  carry  off  the  current  from  the  conductors  sup- 
ported in  the  conduit. 

Slow-Speed  Electric  Motor. — An  electric  motor  having 
the  capacity  to  do  efficient  work  at  a  slow  speed. 

Slow-Speed  Generator. — A  generator  constructed  for 
the  purpose  of  running  at  slow  speed. 

Smashing  Point  of  Incandescent  Electric  Lamp. — A 
time  when  an  incandescent  lamp  has  become  so  dis- 
colored that  it  can  no  longer  render  efficient  service, 
and  it  is  considered  more  economical  to  break  or 
remove  it  and  put  another  in  its  place  than  to  con- 
tinue its  use. 

Smee  Voltaic  Cell. — A  zinc-silver  couple  used  with  an 
electrolyte  of  dilute  sulphuric  acid. 

Smooth-Core  Armature. — A  cylindrical  armature  upon 
whose  even  surface  the  coils  are  wound  as  dis- 
tinguished from  a  slotted  or  iron-clad  armature. 


ELECTRICAL   DICTIONARY  245 

Snap  Switch. — A  switch  so  contrived  as  to  give  a  quick 
break,  a  spiral  spring  being  fastened  between  the 
handle  and  the  arm  in  such  a  manner  that  when  the 
handle  is  drawn  back  to  open  it — the  friction  con- 
tact holding  the  bar — (the  spring  suddenly  pulls 
the  handle  up  and  the  contact  is  broken. 

Snap  Welding  of  Rails. — A  welding  joint  for  rails  ef- 
fective by  clamping  the  rails  together  at  their 
short  projections,  and  then  rapidly  heating  the 
ends  and  pressing  them  together  when  the  re- 
quired degree  of  heat  for  welding  has  been  ob- 
tained. 

Sneak  Current, — A  comparatively  weak  current,  enter- 
ing by  accident  the  circuit  of  a  telephone  or  tel- 
egraph line,  and  from  which  no  instantaneous  bad 
effect  would  result;  yet,  if  permitted  to  continue 
circulating  in  a  bell  or  annunciator  coil,  would 
generate  sufficient  heat  in  a  short  time  to  burn  it 
out.  A  current  not  strong  enough  to  melt  the 
regular  safety  fuses,  yet  of  sufficient  strength  to 
cause  damage  if  permitted  to  continue. 

Sneak  Current  Coil. — A  coil  of  German  silver  wire  em- 
ployed to  cut  a  telephone  apparatus  out  of  circuit 
by  melting  a  drop  of  fusible  metal,  when  a  sneak 
current  or  current  of  dangerous  strength  has 
raised  the  coil  to  a  sufficient  degree  of  heat. 

Socket  for  Electric  Lamp. — A  receptacle  for  an  incan- 
descent lamp. 

Socket  Lamp. — A  lamp  having  a  socket. 
Socket  Switch. — A  socket  key. 

Soft-Drawn  Copper  Wire. — Copper  wire  which  has  been 
first  drawn  and  then  softened  by  annealing. 


246  ELECTRICAL  DICTIONARY 

Soft  Porous  Cell. — A  porous  cell  baked  soft  and  when 

employed  in  a  voltaic  cell  obtains  comparatively 

low  internal  resistance. 
Soldering,  Electric. — A  process  in  which  heat  generated 

electrically  is  employed  to  melt  the  solder  which  is 

used  in  making  the  metallic  joints. 
Soldering  Flux. — Any  solution  serviceable  for  cleaning 

the  surfaces  of  articles  preparatory  to  soldering. 

Solenoid. — A  helical  coil  of  wire,  of  uniform  diameter, 
representing  a  cylinder  and  having  one  end  of  the 
wire  bent  back  and  brought  through  the  center  of 
the  coil,  both  ends  emerging  at  the  same  end.  A 
helical  coil  of  wire  of  uniform  diameter  and  cylin- 
drical in  form. 

Solenoid  Core. — A  core  consisting  ordinarily  of  soft 
iron  introduced  into  a  solenoid ;  and  in  which  posi- 
tion the  magnetic  flux  of  the  magnetizing  current 
magnetizes  it. 

Solid  Arc-Light  Carbon. — Carbon-  electrodes  employed 
in  arc  lamps  which  have  no  core  of  softer  carbon. 
A  carbon  which  is  solid  throughout,  thus  differing 
from  a  cored  carbon. 

Solid-Back  Telephone  Transmitter. — A  form  of  micro- 
phone transmitter  to  a  great  extent  used  in  long 
distance  telephone  service. 

Solid  Thermostat. — A  thermostat  which  depends  for  its 
operation  upon  the  expansion  of  a  solid  body  or 
upon  the  unequal  expansion  of  two  separate  solid 
bodies. 

Solid  Wires. — A  single  wire  conductor,  thus  differing 
from  one  composed  of  a  number  of  parallel  wires. 

Soluble  Electrodes. — Copper,  iron  or  other  metallic  elec- 


ELECTRICAL  DICTIONARY  247 

trodes  which  are  used  in  metallic  electrolysis  and 
which  during  electrolysis  are  converted  into  metal- 
lic salts. 

Solution. — The  action  of  an  attraction  between  one  or 
more  solids  and  a  fluid  when  brought  in  contact, 
by  which  the  former  become  themselves  fluid,  and 
are  diffused  through  the  latter  without  other 
change  or  loss  of  properties. 

Sound. — An  effect  produced  upon  the  brain  through  the 
sense  of  hearing  and  caused  by  the  vibrating 
motion  of  sonorous  bodies. 

Sound  Wave. — Waves  produced  in  an  elastic  medium 
by  the  vibratory  motion  of  sonorous  bodies. 

Sounder  Resonator. — A  sounder  whose  intensity  of 
sound  is  increased  by  resonance;  the  sounder  being 
placed  in  a  resonant  case  for  that  purpose. 

Sounding  Board. — An  elastic  board  possessing  resonant 
properties  and  employed  in  stringed  musical  in- 
struments. 

South  Magnetic  Pole. — The  pole  of  a  magnetic  needle 
which  tends  to  point  to  the  geographical  south  of 
the  earth. 

" Spare"  Machine. — An  additional  machine  of  any  kind 
held  in  reserve  in  a  plant  to  supply  the  place  of 
any  like  machine  which  may  accidentally  become 
disabled. 

Spark  Arrester. — A  screen  made  of  wire  netting,  ad- 
justed around  the  carbon  of  an  arc  lamp  above  the 
globe,  to  obviate  the  scattering  of  sparks. 

Spark  Coil. — A  wire  coil,  insulated  and  connected  with 
the  main  circuit,  and  used  in  a  system  of  electric 
gas  lighting  for  lighting  gas  jets,  which  is  effected 


248  ELECTRICAL  DICTIONARY 

by  means  of  the  spark  produced  by  breaking  the 
circuit. 

Spark,  Electric. — The  phenomena  observed  when  a  dis- 
ruptive discharge  passes  through  a  gap. 

Spark  Gap. — A  space  left  between  the  ends  of  an  elec- 
tric resonator  across  which  the  spark  jumps  when 
a  certain  difference  of  potential  exists  between  two 
opposing  conductors. 

Sparking  Distance. — The  distance  traversed  by  the  dis- 
ruptive discharge  in  its  passage  through  the  air 
space. 

Sparking  of  Dynamo-Electric  Machine. — An  injurious 
production  of  sparks  at  the  commutator  between 
the  brushes  and  commutator  sections  of  a  dynamo 
electric  machine. 

Sparkless  Commutation. — Commutation  of  a  dynamo 
which  is  not  attended  with  sparking  at  the  brushes. 

Speaking  Wire. — A  wire  connecting  two  telephone  ex- 
changes for  the  intercommunication  of  operators 
as  distinguished  from  subscribers'  wires. 

Specific  Conductance. — Specific  conductivity. 

Specific  Conctuctivity. — The  reciprocal  of  specific  resis- 
tance. The  specific  resistance  of  a  certain  length 
and  area  of  cross-section  of  a  body  as  measured 
by  the  same  length  and  area  of  cross-section  of  a 
standard  substance. 

Specific  Gravity. — The  ration  of  the  weight  of  a  body 
to  the  weight  of  an  equal  volume  of  some  other 
body  taken  as  the  unit  or  standard;  water  usually 
being  taken  for  solids  and  liquids,  and  air  for 
gases. 


ELECTRICAL   DICTIONARY  249 

Specific  Heat. — The  capacity  possessed  by  any  mass 
or  body  of  matter  for  heat.  The  capacity  of  a  body 
for  heat  as  compared  with  an  identical  quantity 
of  some  other  body  taken  as  unity. 

Specific  Heat  of  Electricity. — A  proposed  term  to  ac- 
count for  the  heat  absorbed  or  given  out  by  un- 
homogeneous  conductors,  i.  e.,  heat  in  purely  ther- 
mal phenomena  and  heat  in  thermo-electric  phe- 
nomena. 

Specific  Hysteretic  Dissipation. — A  loss  of  energy  per 
unit  of  volume  occasioned  by  hysteresis  in  any  sub- 
stance. A  loss  of  energy  by  hysteresis  in  a  body 
under  specific  conditions  measured  by  a  like  loss 
in  a  standard  body. 

Specific  Magnetic  Conductivity. — The  specific  permea- 
bility of  a  body  to  magnetic  flux. 

Specific  Magnetic  Reluctance. — Specific  magnetic  re- 
sistance. 

Specific  Magnetic  Resistance. — Reluctivity. 

Specific  Magnetism. — A  proposed  term  to  express  the 
quotient  of  the  magnetic  moment  by  its  mass. 

Specific  Resistance. — The  relative  resistance  of  a  sub- 
stance to  the  passage  of  electricity,  as  referred  to 
some  standard  substance.  The  actual  resistance 
of  a  cube  of  a  substance  which  is  one  centimeter  on 
edge,  being  usually  expressed  in  microhms  for 
metals  and  ohms  for  liquids.  Specific  conduction 
resistance. 

Specific  Resistance  of  Liquids. — The  resistance  offered 
by  a  specific  length  and  area  of  cross  section  of 
a  liquid  as  measured  by  the  resistance  of  the  same 
length  and  area  of  cross  section  in  a  standard  con- 
ductor. 


250  ELECTRICAL  DICTIONARY 

Spectrograph. — A  proposed  term  for  radiograph. 

Spectrophone. — An  instrument  used  to  examine  the 
ultra  red  portion  of  the  spectrum. 

Spectroscope. — An  optical  instrument  for  examining 
spectra,  particularly  those  produced  by  flames  in 
which  different  substances  are  volatilized,  so  as  to 
determine,  from  the  position  of  the  spectral  lines, 
the  composition  of  the  substance. 

Spectrum. — The  several  colored  and  other  rays  of  which 
light  is  composed,  separated  by  the  refraction  of  a 
prism  or  other  means,  and  exhibited  either  as 
spread  out  on  a  screen  or  by  direct  vision. 

Speed  Counter. — An  instrument  which  records  the  num- 
ber of  revolutions  which  a  shaft  makes. 

Speed  and  Direction  Indicator. — A  telegraph  employed 
on  shipboard  to  indicate  the  propeller  shaft  revo- 
lution as  to  speed  and  its  movements  as  to  direc- 
tion. 

Speed  Indicator. — A  speed  counter. 

Speed  of  Rotation. — The  number  of  revolutions  made  in 
any  length  of  time.  The  distance  which  the  cir- 
cumference of  a  rotating  wheel  will  pass  over  in  a 
given  time. 

Speed  Recorder. — An  instrument  which  records  instan- 
taneously the  speed  of  a  machine. 

Speeding  of  Dynamo. — Modifying  the  speed  of  a  dy- 
namo in  order  to  get  the  correct  speed  required 
for  the  operation  of  an  electro-receptive  device 
which  has  been  put  into  the  circuit. 

Spelter. — Commercial  zinc. 

Spent  Acid. — Acid  which  has  lost  its  power  of  action 
from  long  use. 


ELECTRICAL  DICTIONARY  251 

Spent  Liquor. — Liquor  such  as  used  in  an  acid  or  bath 
which  has  lost  its  power  of  action  from  long  use. 

Spherical  Aberration. — Incorrect  outlines  of  the  images 
produced  in  a  lens  or  mirror  with  special  faces,  due 
to  a  defect  in  the  curvature  of  one  or  both  of  the 
faces  and  calling  for  as  a  remedy  a  slight  depar- 
ture from  the  true  spherical  form  in  order  to  pro- 
duce a  perfect  image. 

Spherical  Armature. — A  dynamo  armature  whose  coils 
are  wound  on  a  spherical  core. 

Spherical  Candle-Power. — The  average  candle-power 
of  a  luminous  source  in  every  direction.  The  aver- 
age of  a  number  of  observations  taken  at  different 
angles,  the  source  being  moved  about  from  one 
position  to  another. 

Spherical  Candle-Power  Measure. — An  instrument 
which  measures,  or  by  means  of  which  is  measured, 
and  by  a  single  observation,  the  average  spherical 
candle  power  from  a  source  of  light. 

Spherical  Candle-Power  Photometer. — A  photometer 
contrived  for  the  measurement  of  the  average 
spherical  candle-power  of  a  lamp  or  of  any  lumi- 
nous source  from  one  observation  only. 

Spherometer. — An  instrument  for  measuring  the  cur- 
vature of  a  sphere. 

Sphygmograph. — An  instrument  employed  to  record 
the  action  of  the  pulse  and  usually  applied  to  the 
radial  artery  at  the  wrist. 

Sphygmophone. — An  apparatus  embracing  a  michro- 
phone  and  employed  to  examine  the  pulse. 

Spider. — A  radial  bracket  serving  to  support  an  arma- 
ture or  machine  on  a  revolving  shaft. 

Spider  Arm. — A  projection  of  a  spider. 


252  ELECTRICAL  DICTIONARY 

Spiral. — A  term  used  at  times,  signifying  an  open  con- 
ducting coil,  as,  for  instance,  the  primary  or  sec- 
ondary of  an  induction  coil  or  transformer. 

Spiral  Loop  System  of  Distribution. — A  term  used  to 
signify  a  variety  of  parallel  distribution,  employed 
to  obtain  a  uniform  distribution  of  potential,  the 
parallel  conductors  being  extended  in  the  arcs  of 
spirals  throughout  the  district  to  be  served,  from 
the  power  station;  both  spirals  reaching  from  one 
nearly  to  the  other  generator. 

Spiral  Windings. — Solenoidal  winding. 

Splice  Bar. — A  fish  plate  used  in  railroad  construction 
for  joining  the  ends  of  rails. 

Splice  Box. — A  box  which  contains  the  splices  in  elec- 
tric lines  and  underground  cables,  the  splicing  or- 
dinarily being  effected  in  the  boxes. 

Splicing. — Uniting  the  armor  or  protecting  coverings 
of  the  two  ends  of  a  cable  at  a  joint. 

Splicing  Ear. — A  trolley  ear  serving  to  join  the  ends 
of  trolley  wire. 

Split  Battery. — A  battery  of  a  number  of  voltaic  cells, 
connected  in  series,  with  their  central  portion 
grounded  or  connected  to  the  earth. 

Split  Condenser. — A  condenser  designed  by  its  arrange- 
ment for  the  convenient  inter-connection  of  its  dif- 
ferent sections  in  the  same  circuit,  or  for  their  em- 
ployment in  different  circuits  as  occasion  may  de- 
mand. 

Split  Current. — A  current  that  is  divided.  A  current 
taken  from  the  main  telegraph  wire. 

Split  Phase. — The  difference  resulting  in  the  phases  of 
alternating  currents  produced  by  the  division  of  a 
uniphase  alternating  current. 


ELECTRICAL  DICTIONARY  253 

Split-Phase  Motor. — A  multiphase  motor  which  by  the 
introduction  of  a  phase-splitting  contrivance  is 
operated  from  a  Uniphase  alternating-current  cir- 
cuit. A  multiphase  motor  wherein  from  a  single- 
phase  circuit  the  multiphase  currents  are  locally 
produced. 

Split-Secondary  of  Induction  Coil. — A  secondary  of  an 
induction  coil  that  is  divided  into  two  equal  parts. 

Spluttering  of  Arc. — A  spluttering  noise  emanating 
from  a  voltaic  arc  while  it  is  forming. 

Spot. — A  bright  spot  of  light  which  appears  on  the 
scale  of  the  mirror  galvanometer. 

Spotty  Filament. — An  incandescent  lamp  filament 
which  presents  points  of  unequal  brilliancy  when 
raised  to  incandescence  by  the  passage  of  the  cur- 
rent and  which  is  due  to  local  variations  of  resist- 
ance. 

Spreading  the  Magnetic  Field. — Deviation  of  a  mag- 
netic field: 

Sprengal  Mercury  Pump. — An  air  pump,  a  column  of 
mercury  in  which  acts  as  a  piston,  the  actuating 
force  being  the  weight  of  the  column,  which  is  re- 
quired to  exceed  thirty  inches  in  height. 

Spring  Ammeter. — An  ammeter  in  which  the  part 
moved  by  the  current  is  controlled  or  brought  to 
the  zero  position  by  a  spring. 

Spring  Clips  of  Switch. — Spring  clips  of  a  switch  which 
hold  the  blades  when  closed. 

Spring  Contact. — A  spring  connected  to  one  lead  of  an 
electric  circuit,  arranged  to  press  against  another 
spring  or  contact  point  which  it  opens  or  closes. 


254  ELECTRICAL  DICTIONARY 

Spring  Dynamometer. — A  dynamometer  which  depends 
for  its  operation  upon  the  action  of  a  spring. 

Spring  Jack. — A  spring  contact  having  a  hole  in  it  pro- 
vided for  the  introduction  of  a  plug. 

Spring  Relay-Contact. — A  style  of  relay  contact  which 
is  stopped  by  a  spring  when  the  circuit  is  broken. 

Spring  Voltmeter. — A  voltmeter  the  potential  differ- 
ence in  which  is  determined  by  a  magnetic  needle 
moving  against  the  pull  of  a  spring. 

Spurious  Hall  Effect. — A  spurious  electro-motive  force 
caused  in  an  electric  conductor,  through  which  a 
current  is  flowing,  by  variations  in  conductivity  of 
the  conductor  produced  by  a  magnetic  field. 

Spurious  Resistance. — The  counter-electro-motive  force 
operating  to  prevent  a  current  from  being  pro- 
duced to  that  extent  which  would  be  its  full 
strength  were  the  true  resistance  and  actuating 
electromotive  force  only  involved. 

Square  Mil. — A  unit  of  area  equal  to  .000001  square 
inch  and  used  in  the  measurement  of  the  areas  of 
cross  section  in  wires. 

Squirted  Filament. — An  incandescent  lamp  filament  ob- 
tained by  forcing  with  pressure  a  carbonized  car- 
bonaceous composition  through  a  hole  of  proper 
shape. 

Stable  Equilibrium. — That  equilibrium  of  a  body  rest- 
ing upon  a  base,  which  requires  its  center  of  grav- 
ity to  be  raised  in  order  to  upset  it. 

Stage  Regulator. — A  controller  employed  in  a  theater, 
and  located  near  the  stage,  by  means  of  which  the 
incandescent  lamps  can  be  lighted,  extinguished,  or 
their  brilliancy  varied. 


ELECTRICAL  DICTIONARY  255 

Staggering  of  Dynamo  Brushes. — A  term  used  indicat- 
ing a  certain  position  of  the  brushes  on  a  commu- 
tator cylinder,  one  brush  being  set  just  forward  of 
the  other  in  order  that  the  formation  of  the  grooves 
caused  by  wear  may  be  obviated. 

Standard  Candle. — A  standard  of  illuminating  power, 
generally  understood  to  be  the  English  standard 
sperm  candle,  which  when  burning  at  the  rate  of 
two  grains  of  sperm  wax  per  minute  produces  a 
light  of  a  brightness  equal  to  one  candle  power. 

Standard  Compass. — A  compass  employed  on  shipboard 
as  a  standard  with  which  to  compare  and  check 
other  compasses. 

Standard  Earth-Quadrant. — A  length  approximating 
10,000  kilometers,  one-quarter  of  the  earth's  meri- 
dian circle,  through  Paris.  A  unit  of  inductance ; 
the  henry. 

Standard  Luminous  Intensity. — A  unit  of  luminous  in- 
tensity taken  as  a  standard. 

Standard  Megohm. — A  resistance  which  is  equal  to  one 
million  ohms. 

Standard  Ohm. — A  piece  of  pure  copper  wire,  one  cir- 
cular mil  in  diameter,  and  one  foot  long  at  a  certain 
temperature. 

Standard  Resistance. — A  known  resistance  employed  to 
determine  unknown  resistances  by  comparison. 

Standard  Resistance  Coil. — A  coil  having  a  resistance 
of  a  standard  ohm  or  a  multiple  of  a  standard  ohm. 

Standard  Voltaic  Cell. — A  voltaic  cell  employed  as  a 
standard  in  the  measurement  of  unknown  electro- 
motive forces,  by  reason  of  its  own  electromotive 
force  being  practically  constant. 


256  ELECTRICAL  DICTIONARY 

Standard  Wire  Gauge. — A  wire  gauge  adopted  by  the 
National  Electric  Light  Association  and  the  Na- 
tional Telephone  Exchange  Association  of  Amer- 
ica ;  its  gauge  numbers  ranging  from  0000 — .46  inch 
diameter  to  40 — (.00314  inch  diameter. 

Standards. — Supports  located  on  the  roofs  of  buildings 
and  employed  to  support  telephone  wires.  Any 
standard,  such  as  a  resistance  coil  or  voltaic  cell 
used  for  making  comparisons.  The  support  for 
the  bearings  of  a  dynamo  and  some  other  machines. 

Standardized  Resistance  Coil. — A  coil  whose  resistance 
has  been  determined  by  careful  comparison  with 
a  standard. 

Standardizing  a  Voltaic  Cell. — Ascertaining  the  precise 
value  of  a  voltaic  cell's  electromotive  force,  so 
that  it  will  serve  as  a  standard  of  comparison. 

Star  Current  in  Polyphase  System. — In  a  polyphase  sys- 
tem, the  current  between  any  terminal  and  the 
neutral  point,  or  the  current  in  any  branch  of  the 
system. 

Star  Potential  in  Polyphase  System. — In  a  polyphase 
system  the  difference  of  voltmeter  pressure  or  of 
potential  between  any  terminal  and  the  neutral 
point. 

Star  Triphase-Winding. — The  connecting  together  of 
three  triphase  windings  at  a  common  junction,  the 
three  free  ends  being  connected  to  the  terminals. 

Starting  Box. — A  starting  resistance. 

Starting   Box   for   Electric   Motor. — A   resistance    by 

which  an  electric  motor  is  started. 
Starting  Box  of  Shunt-Wound-Motor. — A  box  which 

has  a  rheostat  whose  resistance  is  variable  and  em- 


ELECTRICAL  DICTIONARY  257 

ployed  in  connection  with  the  armature  circuit  of  a 
shunt-wound  motor  in  order  to  impede  the  rush  of 
current  which  attends  the  connection  of  the  motor 
with  the  driving  circuit. 

Starting  Current  of  Motor. — The  current  which  tra- 
verses the  coils  of  a  motor  when  it  first  starts. 

Starting  Motor  for  Synchronous  Motor. — A  small  elec- 
tric motor  serving,  at  times,  to  obtain  the  proper 
speed  for  the  armature  of  a  synchronous  single 
phase  motor  before  making  the  connection  with  the 
driving-current  circuit. 

Starting  Position  of  Street-Car  Controller. — The  posi- 
tion of  a  controller  switch  on  a  street-car  at  which 
the  current  is  first  taken  into  the  motors  at  start- 
ing. 

Starting  Rheostat. — Coils  of  wire  mounted  and  con- 
nected so  that  they  can  be  introduced  in  the  circuit 
of  a  motor  in  succession  while  it  is  being  started. 

Starting  Torque  of  Motor. — -The  torque  necessary  to 
start  a  motor  and  that  which  is  developed  by  the 
motor  when  starting. 

Static  Breeze. — The  silent  or  brush  discharge  of  high 
tension  electricity. 

Static  Discharge. — Disruptive  discharge. 

Static  Electricity. — Electricity  generated  by  friction. 

Static  Energy. — That  energy  which  a  body  possesses 
when  at  rest  due  to  advantage  of  position  or  other 
causes,  such  as  the  stress  of  a  spring  or  the  foot 
pounds  of  a  pound  weight  supported  a  certain  num- 
ber of  feet  above  a  plane. 

Static  Hysteresis. — ,A  phenomenon  of  magnetization  of 
iron  attributed  to  molecular  friction,  by  reason  of 


258  ELECTRICAL  DICTIONARY 

which  considerable  energy  is  expended  during 
every  reversal  in  its  magnetization  as  contradistin- 
guished from  viscous  hysteresis. 

Static  Shock. — A  term  in  electro-therapeutics  for  a 
method  of  applying  static  discharges  from  small 
condensers  or  Leyden  jars  to  a  patient  who  is  in- 
sulated from  the  ground  with  one  electrode  ap- 
plied to  the  conducting  surface  on  which  he  rests, 
while  the  other,  spherical  electrode,  is  brought  near 
the  body  so  as  to  produce  a  disruptive  or  spark 
discharge. 

Static  System  of  Induction  Telegraphy. — A  mode  of 
electric  communication  without  any  metallic  con- 
nection between  the  stations;  but  which  depends 
upon  static  induction  between  the  instruments  for 
sending  and  receiving.  Wireless  telegraphy. 

Static  Transformer. — A  term  used  to  distinguish  the 
ordinary  transformer  from  a  rotary  transformer. 

Statics. — That  branch  of  mechanics  which  treats  of  the 
equilibrium  of  forces,  or  relates  to  bodies  as  held 
at  rest  by  the  forces  acting  on  them ;  in  distinction 
from  dynamics,  or  the  science  of  forces  producing 
motion. 

Static  Circuit-Breaker.— 4A  circuit  breaker  employed  in 
a  central  station. 

Station  Load. — The  entire  load  on  a  central  station  at 
any  time. 

Station  Load-Curve. — A  curve  which  represents  the 
station  load  at  any  time. 

Station  Recording- Wattmeter. — A  wattmeter  adaptable 
for  central  stations  for  the  purpose  of  recording 
the  energy  delivered. 


ELECTRICAL  DICTIONARY  259 

Station  Transformer. — A  transformer  used  in  a  central 
station,  or  one  which  supplies  a  load  in  a  station. 
A  transformer  designed  to  furnish  the  current  for 
potential  indicators  and  lamps  on  the  station 
switchboard. 

Stationary  Transformers. — A  term  used  to  signify  alter- 
nating-current transformers  as  contradistinguished 
from  rotary  transformers. 

Stationary  Electric  Motor. — An  electric  motor  firmly 
attached  to  the  ground  or  floor  as  contradistin- 
guished from  one  which  moves  about. 

Stationary  Tachometer. — A  tachometer  which  indicates 
the  number  of  revolutions  per  minute  of  a  shaft  in 
a  stationary  rotating  machine. 

Stator. — The  stationary  portion  of  a  rotary  field  induc- 
tion motor  in  distinction  from  the  portion  which 
rotates. 

Stator  Armature. — A  dynamo  or  motor  armature  which 
remains  at  rest  while  the  machine  is  in  operation. 
A  part  of  a  machine  which  is  at  once  its  armature 
and  immovable. 

Statute  Mile. — -A  British  statute  mile  equal  to  5,280  feet. 
Steady  Current. — A  current  whose  strength  is  fixed  or 
invariable. 

Steam  Governor,  Electric. — An  electric  device  whose 
employment  in  connection  with  a  valve  regulates 
the  supply  of  steam  to  an  engine  so  that  the  engine 
is  driven  at  a  speed  such  as  to  maintain  a  constant 
potential  or  a  constant  current. 

Steam-Turbine  Dynamo. — A  dynamo  of  high  speed,  a 
steam  turbine  being  employed  to  drive  the  arma- 
ture. 


260  ELECTRICAL  DICTIONARY 

Steering  Compass. — A  compass  provided  on  shipboard 

for  steering  a  ship. 

Steering,  Electric. — Steering  by  means  of  electricity. 
Step-Down  Converter. — A  step-down  transformer. 

Step-Down  Transformer. — A  transformer  which  trans- 
forms a  small  current  of  great  difference  of  poten- 
tial into  a  large  current  of  small  difference  of  po- 
tential. 

Step-Up  Converter. — A  step-up  transformer. 

Step-Up  Transformer. — A  transformer  which  trans- 
forms a  large  current  of  small  difference  of  poten- 
tial into  a  small  current  of  great  difference  of  po- 
tential. 

Stereopticon. — An  instrument  provided  with  a  lantern 
and  other  accessories  and  used  to  project  the 
images  of  objects  upon  a  screen  so  that  they  stand 
out  in  relief. 

Sterilization,  Electric. — A  mode  of  sterilizing  solutions, 
which  consists  in  destroying  the  germs  by  means  of 
electric  currents. 

Stethoscope. — An  instrument  for  ascertaining  the  condi- 
tion of  the  heart,  lungs,  and  system  of  circulation 
generally  by  the  sound  they  produce. 

Sticking  of  Magnetic  Armature. — The  adherence  after 
the  current  is  cut  off  of  the  armature  to  the  poles 
of  the  magnet. 

Stiff  Field. — A  magnetic  field  whose  density  is  compar- 
atively great. 

Stock  Ticker. — An  instrument  employed  in  brokers'  of- 
fices and  elsewhere  for  receiving  quotations  and 
other  information  by  means  of  printing  appearing 


ELECTRICAL  DICTIONARY  261 

upon  a  ribbon  of  paper  which  is  fed  from  the  in- 
strument. 

Stock-Ticker  Service. — The  service  which  supplies  stock 
quotations  from  the  stock  exchange  to  subscrib- 
ers. 

Stopper  Incandescent  Lamp. — An  incandescent  lamp 
having  the  filament  mounted  in  the  chamber  of  a 
closely  fitting  stopper  instead  of  by  being  sealed 
hermetically  in  the  lamp  chamber. 

Storage  Accumulator. — A  storage  battery. 

Storage  Battery. — A  group  consisting  of  a  number  of 
distinct  storage  cells  so  connected  together  as  to 
form  a  single  electric  service. 

Storage  Battery  Car. — A  motor  propelled  car  whose  mo- 
tor receives  its  current  from  storage  batteries.  A 
car  used  to  convey  storage  batteries. 

Storage  Battery  Meter. — A  meter  employed  in  connec- 
tion with  a  storage  battery  and  serving  to  indicate 
the  quantity  of  electric  energy  remaining  in  the 
battery. 

Storage  Battery  Traction. — Car  traction  electrically 
created  by  means  of  storage  batteries. 

Storage  Capacity. — A  name  signifying  the  ampere 
hours  of  electricity  which  can  be  obtained  from  a 
storage  battery  in  current  form. 

Storage  Cell. — Two  plates  of  metal  or  compounds  of 
metal  whose  chemical  relations  are  changed  by  the 
passage  from  one  plate  to  the  other  of  an  electric 
current  through  an  electrolyte  into  which  they  have 
been  immersed.  A  term  applied  to  a  jar  which  con- 
tains but  one  cell. 

Storage  of  Energy. — The  transformation  from  kinetic 
to  potential  energy. 


262  ELECTRICAL  DICTIONARY 

Stranded  Conductor. — A  conductor  which  consists  of  a 
number  of  fine  twisted  conductors  and  designed 
either  to  obtain  greater  flexibility  or  to  reduce  self- 
induction  or  Foucault  currents. 

Strap  Key. — A  key  for  which  a  strap  of  metal  is  used 
in  the  manufacture. 

Strap  Switch. — A  switch  for  which  a  strap  of  metal  is 
used  in  the  manufacture. 

Stratification  Tube.— A  tube  which,  through  a  high 
vacuum,  shows  the  stratification  of  the  electric 
discharge.  A  Geissler  tube. 

Stray  Currents. — Eddy  currents.    Foucault  currents. 

Stray  Field. — In  a  dynamo  or  motor  the  section  of  the 
field  whose  lines  of  force  or  magnetic  flux  leakage 
are  not  passed  through  by  the  armature  windings. 

Stray  Flux.— The  flux  of  a  stray  field. 

Street  Car  Controller. — An  electrical  device  enclosed 
in  a  box  on  the  car-platform  and  serving  to  regu- 
late the  speed  of  an  electric  car. 

Street-Car  Lamp. — An  incandescent  lamp  whose  fila- 
ment is  anchored  and  adaptable  for  use  in  street 
cars. 

Street-Car  Motor. — A  motor  used  to  propel  trolley  cars. 

Street-Car  Recording  Wattmeter. — A  wattmeter  de- 
signed for  recording  the  supply  of  energy  received 
by  a  street-car  in  a  specified  length  of  time. 

Street  Load-Diagram. — A  diagram  made  to  show  the 
electric  load  on  the  different  streets  in  a  district 
supplied  with  electricity. 

Street  Mains. — The  conductors  in  a  system  of  electric 
distribution,  which  extend  through  the  streets  be- 
tween the  different  junction  boxes  and  which  serve 


ELECTRICAL  DICTIONARY  263 

to  distribute  the  current  from  the  feeders  and  with 
which  service  wires  are  connected. 

Street  Railway,  Electric. — A  street  railway  which  is 
operated  by  electricity  or  power  supplied  elec- 
trically. 

Street  Service. — That  part  of  a  circuit  in  a  system  of  in- 
candescent lamp  distribution  which  extends  from 
the  main  to  the  cut-outs,  and  which  is  external  to 
the  building  or  structure  supplied. 

Strength  of  Current. — Amperage — (Quality  of  current 
in  a  circuit. 

Strength  of  Magnetic  Field. — The  intensity  of  a  mag- 
netic field  at  any  point  determined  by  the  force 
with  which  it  acts  on  a  unit  magnet  pole  located  at 
that  point. 

Stress. — Force  acting  upon  a  solid  body  by  pull,  pres- 
sure or  in  other  ways,  and  which  produces  distor- 
tion or  strain. 

Stress  Flux. — Flux  from  whose  action  a  stress  results. 

Striking  an  Arc. — 'Moving  the  carbon  electrodes  apart 
in  order  to  form  an  arc  between  them. 

Striking  Bath. — A  bath  used  in  silver  plating  and  which 
contains  a  larger  proportion  of  free  cyanide  than 
of  silver,  thus  obtaining  instantly  a  deposit  upon 
the  object  to  be  plated,  before  it  is  placed  in  the 
regular  plating  bath. 

Striking  Distance. — Sparking  distance.  The  distance 
which  a  disruptive  charge  will  traverse. 

Striking  Mechanism  of  Arc  Lamp. — Mechanism  which 
separates  the  carbons  in  an  arc  lamp  when  the  arc 
is  formed. 

Strip  Fuse. — A  safety  strip. 


264  ELECTRICAL  DICTIONARY 

Strip  Resistance. — lA  resistance  in  which  strip  conduc- 
tors are  employed. 

Stripping  Liquid. — The  liquid  in  a  stripping  bath.  The 
liquid  used  in  the  process  of  removing  the  super- 
ficial layer  of  one  metal  from  the  surface  of  another 
by  electrolysis. 

Strong-Current  Arrester. — An  arrester  adaptable  for 
the  protection  of  a  line  against  currents  resulting 
from  contact  with  a  trolley  circuit  or  any  other 
circuit  of  strong  current. 

Struck. — A  term  in  electro-plating  used  in  relation  to 
metallic  surfaces  which  have  been  electrolytically 
covered  with  a  film  of  silver  or  nickel  by  immersion 
in  a  bath  and  exposure  for  a  few  seconds  to  the 
action  of  a  strong  current. 

Structural  Carbon. — A  lamp  filament  produced  by  car- 
bonizing any  structural  material  capable  of  being 
carbonized,  as  bamboo  for  instance. 

Structureless  Carbons. — Lamp  filaments  produced  by 
carbonizing  structureless  materials,  as  for  instance 
tamine  and  other  materials. 

Sub-Aqueous  Cable. — A  cable  used  in  sub-aqueous 
work  usually  in  fresh  water.  Cables  used  in  rivers 
in  distinction  from  sub-marine  or  ocean  cables. 

Sub-Center  Transformer. — A  transformer  located  at  a 
sub-center  of  distribution  and  which  supplies  sec- 
ondary circuits  radiating  therefrom. 

Sub-Divided  Conductor. — A  multiple-wire,  stranded  or 
composite  conductor. 

Sub-Divided  Transformer. — A  transformer  in  whose 
primary  or  secondary  coils  there  are  subdivisions. 
A  transformer  whose  magnetic  circuit  is  subdi- 
vided. 


ELECTRICAL  DICTIONARY  265 

Sub-Exchange  for  Telephones. — »A  subordinate  ex- 
change. A  local  exchange  operating  under  a  cen- 
tral exchange. 

Sub-Mains. — Branch  conductors  from  mains. 

Sub-Marine. — Under  the  sea. 

Sub-Marine  Boat,  Electric. — A  boat  so  constructed  as  to 
be  driven  and  steered  under  water. 

Sub-Marine  Cable. — A  cable  intended  for  use*  under  the 
ocean. 

Sub-Marine  Finder. — A  proposed  form  of  induction  bal- 
ance for  locating  submerged  bodies  or  objects  of 
metal,  such  as  ships,  anchors,  torpedoes,  etc. 

Sub-Marine  Fuse. — A  fuse  serving  to  ignite  and  explode 
a  sub-marine  mine. 

Sub-Marine  Key. — A  key  employed  in  sub-marine  tele- 
graphic operations. 

Sub-Marine  Mine. — A  mass  of  highly  explosive  material 
confined  in  water-tight  metallic  receptacles  and 
sunk  in  the  water  for  the  purpose  of  destroying  by 
an  explosion  the  vessel  of  an  enemy  which  may 
pass  over  them. 

Sub-Marine  Search  Light. — An  incandescent  light  serv- 
ing to  explore  under  water. 

Sub-Marine  Sentry. — A  water  kite,  situated  under  a  ves- 
sel, and  employed  in  sub-marine  cable  work  to  in- 
dicate very  shallow  places  in  the  water,  by  rising 
to  the  surface  when  touching  sea-bottom. 

Sub-Marine  Telegraphy. — Trans-oceanic  telegraphy.  A 
system  of  telegraphy  employing  a  sub-marine  cable 
as  a  line  wire. 

Sub-Marine  Telephony. — Telephony  effected  by  the  use 
of  sub-marine  cables. 


266  ELECTRICAL  DICTIONARY 

Sub-Permanent  Magnetism. — A  term  applied  to  magnet- 
ism present  in  an  iron  ship  and  meaning  that  such 
magnetism  is  not  as  marked  as  that  present  in  a 
bar  of  magnetized  steel. 

Sub-Station. — An  auxiliary  station. 

Sub-Station  Accumulator. — An  accumulator  used  at 
sub-stations. 

Sub-Station  Transformer. — A  transformer  used  at  sub- 
stations. 

Subway,  Electric. — An  underground  passage  way  util- 
ized to  receive  electric-light  wires  or  cables. 

Sulphating. — In  storage  battery  cells,  the  formation  of 
a  hard,  white  basic  sulphate  due  to  over-exhaustion 
of  the  cells  resulting  in  a  loss  in  the  operation  of 
the  cells. 

Sunflower  Commutator. — A  commutator  whose  appear- 
ance resembles  that  of  a  sunflower.  A  style  of  disc 
commutator. 

Sun-Light  Color- Values. — 'Luminous  frequencies  which 
give  to  the  light  of  an  artificial  source  the  same  ef- 
fects which  sunlight  produces. 

Sun-Spot  Disturbance. — Disturbance  due  to  the  pres- 
ence of  spots  on  the  sun. 

Sun-Spots. — Dark  areas  which  are  observed  at  times  on 
the  sun's  surface. 

Sun-Stroke,  Electric. — Effects  due  to  exposure  to  the 
arc  light  and  similar  to  those  produced  by  sun- 
stroke. 

Sun  Telegraph. — /The  heliograph. 

Sunk  Winding. — An  iron-clad  winding.  A  winding 
made  in  slots  or  grooves  and  buried  below  the  sur- 
face of  an  armature. 


ELECTRICAL  DICTIONARY  267 

Superposed  Magnetism. — A  term  which  characterizes 
a  magnetism  impressed  on  a  substance  which  has 
already  been  magnetized. 

Super-Saturation. — The  condition  assumed  by  a  solu- 
tion which  has  cooled  below  its  solidifying  point 
while  not  exposed  to  air. 

Super-Saturation  of  Solution. — The  condition  obtained 
when  a  warmed  saturated  solution  of  salt,  con- 
tained in  a  tight  vessel,  has  cooled  without  ex- 
posure to  the  air,  being  shaken. 

Supplement  of  Angle. — That  which  is  required  to  bring 
the  value  of  an  angle  to  180  degrees. 

Supplementary  Dynamo. — A  term  signifying  a  booster 
dynamo. 

Supply  Meter,  Electric. — A  meter  whose  function  is  to 
measure  the  supply  of  electricity  furnished  to  a 
machine  or  a  purchaser. 

Support  Plate  of  Storage  Cell. — A  storage  cell's  grid. 

Surface  Action. — Action  confined  to  a  surface. 

Surface  Contact  of  Street-Railway  Car. — A  contact 
which  is  situated  on  a  level  with  the  street  surface 
and  designed  for  use  in  an  electric  street  railway 
system  in  connection  with  the  driving  of  the  cars. 

Surface  Contact  Street  Railway  System. — A  third  rail 
system.  An  electric  street  railway  system  in  which 
surface  contacts  are  used. 

Surface  Integral  of  Magnetic  Induction. — The  entire 
volume  of  magnetic  flux  which  passes  through  a 
surface. 

Surface-Wound  Armature. — An  armature  wound  upon 
its  surface,  the  conductors  lying  on  the  surface  of 


ELECTRICAL  DICTIONARY 

its  coil,  instead  of  being  wound  in  grooves  like  the 
iron-clad  armature. 

Surgical  Lamp. — A  lamp  used  by  surgeons  for  examin- 
ing and  operating  upon  the  human  body. 

Surgical  Circuit. — A  circuit  having  a  surging  discharge 
passing  through  it. 

Surging  Discharge. — The  disruptive  or  sudden  dis- 
charge of  such  a  static  condenser  as  a  Ley  den  jar, 
or  of  any  other  charged  conductors;  the  discharge 
being  oscillatory  in  character. 

Surgings,  Electric. — Oscillating  vibrations  present  in  a 
conductor  which  is  rapidly  discharging  or  being 
charged.  Direct  or  induced  electric  oscillations. 

Susceptance. — A  quantity,  in  an  alternating-current 
circuit  conductor,  whose  square  plus  the  square  of 
conductance  equals  the  square  of  admittance. 

Suspended-Coil  Galvanometer. — A  galvanometer  with  a 
suspended  coil  by  the  movements  of  which  a  cur- 
rent passing  through  it  is  measured. 

Suspension. — The  mechanism  by  which  anything  is  sus- 
pended. The  means  by  which  any  apparatus  or  ac- 
cessory thereto  is  suspended,  as  for  instance  a  car- 
motor,  pendulum,  needle,  etc. 

Suspension  for  Car-Motor. — The  means  by  which  a  car- 
motor  is  kept  in  position  on  the  truck  of  a  car. 

Swage. — A  tool  variously  shaped  or  grooved  on  the 
end  or  face  and  used  by  workers  in  metals  for  shap- 
ing their  work,  whether  in  sheet  metal  or  forging, 
by  holding  the  tool  upon  the  work  or  the  work 
upon  the  tool  and  striking  with  a  sledge. 

Swage. — To  shape  heated  metals  by  means  of  a  swage ; 
to  fashion,  as  a  piece  of  iron,  by  drawing  or  ham- 


ELECTRICAL  DICTIONARY  269 

mering  it  into  a  groove  or  mould  having  the  re- 
quired shape. 

Swaging. — The  shaping  of  heated  metals  by  drawing  or 
hammering  them  into  a  tool  having  the  required 
shape. 

Swaging,  Electric. — Swaging  metals  while  softened  by 
electric  heat  (see  swaging). 

Sweating. — A  process  by  which  the  ends  of  electric- 
light  cables  are  soldered  together. 

Swinging  Cross. — A  term  applied  to  an  intermittent 
cross. 

Swinging  Earth. — A  term  applied  to  an  intermittent 
earth. 

Swinging  Voltmeter. — A  voltmeter  which  can  be  read 
from  any  direction,  being  supported  on  a  swinging 
bracket  attached  to  a  switchboard. 

Switch. — A  device  for  opening  and  closing  an  electric 

circuit. 

Switch-Bell. — A  switch  and  bell  combined. 
Switch  Blade. — The  blade  of  a  switch.    A  conducting 

strip. 

Switch-Board. — A  board  or  tablet  to  which  wires  are 
led  connecting  with  cross  bars  or  other  switching 
devices,  so  as  to  allow  connections  to  be  made  with 
other  circuits  or  between  themselves.  A  board 
equipped  with  switches  and  instruments  which 
serve  to  control  a  distribution  system  and  the  gen- 
erators employed  in  it.  A  board  equipped  with 
switches  for  opening  or  closing  or  interchanging 
electric  circuits  connected  with  it. 

Switch-Board  Fittings. — A  general  term  applied  to  the 
divers  fittings  or  accessary  devices  of  a  switch- 


270  ELECTRICAL  DICTIONARY 

board,  such  as  connectors,  set-screws,  wire-holders 
or  bus-bar  connections,  by  means  of  which  the  dif- 
ferent apparatuses  are  placed  upon  the  board, 

Switch-Board  Transformers. — Transformers  serving  on 
an  alternating-current  switch  board  to  furnish  lo- 
cally alternating  currents  of  reduced  pressure. 

Switch-Board  Wattmeter. — A  wattmeter  mounted  on  a 
switch  board  and  whose  functions  is  to  indicate  the 
quantity  of  energy  which  some  circuit  connected 
therewith  puts  out  or  takes  in. 

Switched-In. — Placed  in  a  circuit  by  the  manipulation 
of  a  switch. 

Switched-Out. — Kemoval  from  a  circuit  by  the  manipu- 
lation of  a  switch. 

Swivel  Clevis. — A  nut  and  bolt  contrivance  used  to  take 
up  slack  in  guy-rods. 

Symmetrical  Alternating  Current.— An  alternating  cur- 
rent, the  suggestive  alternations  of  which  have  op- 
posite values  but  equal  to  each  other,  differing  only 
with  respect  to  direction. 

Symmetrical  Magnetic  Field. — A  field  of  symmetrically 
distributed  magnetic  flux. 

Symmetrical  Polyphase  System. — A  polyphase  system 
which  with  respect  to  pressures,  conductors,  cur- 
rents and  loads  is  symmetrically  arranged. 

Sympathetic  Electric  Vibrations. — Electric  vibrations 
which  the  electro-magnetic  waves  sent  out  by  one 
circuit  produces  in  another.  Electric  vibrations 
due  to  resonance. 

Synchronism. — Occurrence  of  two  or  more  events  simul- 
taneously. Unison  of  recurrence  in  apparatus  of 


ELECTRICAL.  DICTIONARY  271 

alternating-current  systems  occurring  at  the  same 
time. 

Synchronize. — To  agree  in  time ;  to  be  simultaneous.  To 
effect  concurrence  or  unison  and  coincidence  of 
phase  in  two  alternating-current  machines  in  order 
to  connect  them  together  electrically. 

Synchronizer. — That  which  causes  synchronism.  A  con- 
trivance which  indicates  when  synchronism  has 
been  reached  in  alternators  to  be  connected  in  par- 
allel. 

Synchronizing  Dynamo-Electric  Machine. — The  act  of 
adjusting  the  recurrences  and  phases  of  two  alter- 
nating-current dynamos  in  order  that  they  may  be 
connected  in  parallel. 

Synchronizing  Torque. — The  torque  which  tends  to 
bring  into  synchronism  its  own  alternating-current 
generator  armature  with  some  other  armature  oper- 
ating with  it. 

Synchronous. — 'Simultaneously  occurring,  usually  un- 
derstood as  co-periodic  and  co-phasal  in  distinction 
from  periodic  agreement  only. 

Synchronous  Generator, — An  alternating-current  gen- 
erator capable  of  synchronous  operation  with  an- 
other generator. 

Synchronous  Motor. — An  alternating-current  motor 
which  will  operate  properly  only  after  being 
brought  into  step  with  the  driving  current. 

Synchronous  Multiplex  Telegraphy. — A  system  of  teleg- 
raphy in  which  a  number  of  messages  are  transmit- 
ted simultaneously  over  a  single  wire,  all  in  one 
direction,  or  some  in  one  direction  and  some  in  the 
opposite. 


272  ELECTRICAL  DICTIONARY 

Synchronous  Vibrations. — Vibrations  excited  by  several 
distinct  systems  which  are  in  exact  unison  both  in 
recurrence  and  phase. 

Synthesis. — The  uniting  of  elements  to  form  a  com- 
pound. The  opposite  of  analysis. 


T. 

T-Connector. — A  connector  similar  in  shape  to  the  let- 
ter T  and  serving  to  conect  a  wire  with  two  branch 
wires. 

Table  Push. — A  push  button  connected  with  a  call-bell 
and  located  on  a  table  for  convenience  in  ringing. 

Tablet  Board. — A  panel  switchboard  or  one  divided  into 
tablets. 

Tachograph. — An  instrument  which  records  the  number 
of  revolutions  made  in  a  machine  or  shaft  per  min- 
ute. 

Tachometer. — An  instrument  for  measuring  the  velocity 
and  variations  of  velocity  of  machines  and  shafts 
and  indicating  on  a  dial  the  number  of  these  revo- 
lutions per  minute. 

Tail  of  Mercury. — A  trail  left  behind  a  drop  of  impure 
mercury  when  drawn  over  a  surface,  indicating  the 
presence  of  oxides. 

Tailings. — In  a  telegraph  line,  the  prolongation  of  a 
current  at  the  remote  receiving  station  due  to  self- 
induction  and  the  discharge  of  the  line.  The  inter- 
ference with  the  definiteness  of  signal  marks  due  to 
retardation  in  high  speed  transmission  of  telegraph 
signals  by  the  automatic  system.  Residual  dis- 


ELECTRICAL  DICTIONARY  273 

charges  through  the  receiving  instrument  from  the 
line  producing  wrong  marks. 

Talking  Circuit. — A  circuit  in  a  telephone  system  which 
a  subscriber  uses  during  conversation  in  distinc- 
tion from  a  circuit  used  for  calling. 

Tamadine. — A  form  of  cellulose,  used  for  making  the 
filaments  of  an  incandescent  lamp  by  cutting  the 
material  into  proper  shapes  and  then  carbonizing 
them. 

Tangent. — A  right  line  touching  an  arc  at  one  extrem- 
ity and  terminated  by  a  secant  passing  through 
the  other  extremity. 

Tangent  and  Sine  Galvanometer. — A  galvanometer  pro- 
vided with  two  magnetic  needles  differing  in 
length,  the  shorter  serving  to  measure  tangents 
and  the  longer  being  used  for  sine  measurements 
of  current  strength. 

Tangent  Scale. — An  arc  of  a  circle  wherein  the  number 
of  graduations  in  any  arc  commencing  at  zero  are 
proportional  to  the  tangent  of  the  angle  which  such 
arc  subtends;  thus,  the  scale,  instead  of  being  di- 
vided into  degrees,  is  divided  into  arcs  of  varying 
lengths,  which  obviates  the  necessity  of  consulting 
tables  to  find  tangents  corresponding  to  the  de- 
grees. 

Tanning,  Electric. — The  tanning  of  leather  by  means  of 
electric  currents. 

Tap. — A  conductor  connected  to  a  larger  conductor  as 
a  shunt.  A  derived  circuit  serving  to  carry  off  a 
portion  of  a  main  current. 

Tap  Wires. — The  conductors  serving  in  trolley  systems 
to  take  the  current  from  the  mains  at  a  pole  to  an 
adjacent  point  on  the  trolley  wire. 


274  ELECTRICAL  DICTIONARY 

Taped  Wire. — A  wire  insulated  with  a  material  similar 
in  form  to  tape,  or  insulated  with  a  suitable  ma- 
terial and  then  wound  with  tape. 

Taping. — Wrapping  insulated  tape  around  a  wire  or 
joint. 

Taps. — Branches  which  connect  with  mains  and  are 
taken  from  them  into  the  different  apartments  and 
to  the  fixtures  in  a  building  supplied  by  a  system 
of  incandescent  lamp  distribution. 

Target,  Electric. — A  target  which  registers  automatical- 
ly by  means  of  electricity  the  points  struck  by  a 
ball. 

Teaser,  Electric. — A  fine  wire  coil  wound  on  the  field 
magnets  of  a  dynamo  in  shunt  with  the  regular 
magnet. 

Teaser  Winding. — An  extra  coil  with  which  the  arma- 
ture of  a  monocyclic  generator  is  wound  and  con- 
sisting of  less  turns  and  smaller  cross-section  than 
the  main  winding,  one  end  ol  it  being  connected  to 
a  collecting  ring,  while  the  other  is  connected  with 
the  center  of  the  main  winding. 

Teeth  of  Armature. — Ridges  projecting  from  the  sur- 
face of  an  armature  core  in  which  the  armature 
conductors  rest. 

Tel-Autograph. — A  system  of  telegraphy  by  means  of 
which  the  reproduction  of  writing  in  fac-simile  is 
effected  at  a  distance. 

Tele-Barograph. — An  instrument  which  records  the  in- 
dications of  a  barometer  at  a  distance. 

Tele-Barometer,  Electric. — A  barometer  which  records 
by  means  of  electricity  the  indications  of  baromet- 
ric pressure  at  a  distance. 


ELECTRICAL  DICTIONARY  275 

Telegraph. — An  instrument  or  apparatus,  or  a  process 
for  communicating  intelligence  rapidly  between 
distant  points  by  employing  signs  representing 
words  or  ideas  and  transmitted  by  means  of  elec- 
tricity over  conductors. 

Telegrapher's  Cramp. — A  disease  of  the  hand  sometimes 
contracted  by  telegraph  operators  and  caused  by 
the  too  excessive  use  of  the  muscles  of  the  hand  in 
telegraphing. 

Telegraphic  Box-Sounder. — A  sounder  having  its  re- 
ceiving magnets  confined  in  a  resonant  box  in  order 
that  the  intensity  of  the  sound  may  be  increased. 

Telegraphic  Interrupter. — A  defect  in  a  line  which  in- 
terferes with  the  transmission  of  telegraphic  com- 
munications. 

Telegraphic  Key. — A  key  or  switch  used  by  an  operator, 
by  means  of  which  he  makes-and-breaks  the  cir- 
cuit in  a  manner  to  correspond  to  the  dots  and 
dashes  of  the  Morse  alphabet. 

Telegraphic  Repeater. — An  extension  of  the  relay  sys- 
tem adopted  for  long  lines.  An  instrument  which 
causes  the  telegraphic  apparatus  in  a  station  to  re- 
peat the  message  into  another  circuit. 

Telegraphic  Stock-Printer. — An  instrument  which 
prints  on  ribbons  of  paper  the  quotations  of  stock 
transmitted  from  the  stock  exchange. 

Telegraphic  Time-Service. — Time  distribution  by  tele- 
graph. Time  sent  out  to  subscribers  from  a  stand- 
ard clock  by  means  of  electricity. 

Tele-Hydro-Barometer. — An  instrument  employed  to 
record  and  indicate  at  a  distance  the  height  of 
liquids  in  a  vessel  or  receptacle. 


276  ELECTRICAL  DICTIONARY 

Tele-Hydro-Barometer,  Electric. — An  instrument  em- 
ploying electricity  to  effect  the  record  and  regis- 
tration of  the  height  of  liquids  in  a  vessel  or  re- 
ceiver at  distant  stations. 

Telephone. — An  instrument  which  transmits  articulate 
speech  by  means  of  electricity. 

Telephone  Battery. — Any  style  of  open-circuit  battery 
which  can  be  adapted  to  use  in  telephone  service. 

Telephone  Cable. — A  cable  either  overhead  or  under 
ground  which  is  adaptable  for  the  transmission  of 
telephonic  messages. 

Telephone  Call-Bell. — A  bell  serving  to  call  the  person 
with  whom  the  subscriber  desires  to  speak. 

Telephone  Call- Wire. — A  wire  used  in  some  systems  by 
means  of  which  a  subscriber  is  enabled  to  call  up 
the  central  office.  A  special  wire  for  calling. 

Telephone  Cords. — Flexible  cords  used  for  the  conven- 
ient moving  about  of  telephone  receivers  and  for 
other  purposes. 

Telephone  Cross-Talk. — An  interference  in  a  circuit  re- 
sulting from  induction  or  leakage  from  an  ad- 
jacent circuit. 

Telephone  Drop. — A  contrivance  corresponding  to  an 
annunciator  drop  and  employed  on  a  switchboard. 

Telephone  Exchange. — A  central  station  fully  equipped 
with  circuits,  switches  and  all  the  other  accessories 
of  a  complete  apparatus,  which  are  employed  to 
place  subscribers  in  communication  with  each 
other,  or  with  another  exchange. 

Telephone-Exchange  Switchboard. — A  central  station 
switchboard  by  means  of  which  subscribers  are 
readily  placed  in  connection  with  each  other. 


ELECTRICAL  DICTIONARY  277 

Telephone  Galvanometer. — A  galvanometer  of  high  re- 
sistance, comprising  an  electro-magnet  with  a  thin 
plate  or  disc  of  iron  carefully  adjusted  between  its 
poles  and  bridged  permanently  across  the  circuit 
of  a  telephone  in  order  that  visual  call-signals  may 
be  given. 

Telephone  Head-Gear. — An  appliance  for  the  head  en- 
abling a  telephone  receiver  to  be  attached  conven- 
iently to  the  ear  of  the  operator. 

Telephone  Repeating-Coil. — A  style  of  induction  coil 
serving  to  repeat  telephonic  messages.  An  induc- 
tion coil  provided  with  an  insulated  winding  in 
each  of  the  two  circuits  to  be  connected. 

Telephone  Set. — A  term  in  its  usual  application  signify- 
ing the  apparatus  which  a  telephone  subscriber 
uses  at  his  business  place  or  home. 

Telephone  Tinnitus. — A  nervous  disorder  of  the  audi- 
tory sense  caused  by  continual  use  of  the  telephone. 

Telephone  Transformer. — An  instrument  which  serves 
to  repeat  a  telephonic  message  from  one  circuit  into 
another. 

Telephonic  Receiver. — That  part  of  a  telephone  appara- 
tus which  is  used  to  receive  the  message  by  placing 
it  in  contact  with  the  ear. 

Telescope. — An  optical  instrument  employed  in  view- 
ing distant  objects  and  which  enlarges  the  visual 
angle  under  which  they  are  seen,  thus  increasing 
their  apparent  dimensions. 

Temper. — To  render  metals  hard  and  elastic  by  sudden- 
ly cooling  them  while  heated. 

Temperature. — Condition  with  respect  to  heat  or  cold 
as  indicated  by  the  sensations  produced  or  by  the 
thermometer  or  pyrometer.  Degree  of  heat  or  cold. 


278  ELECTRICAL  DICTIONARY 

Temperature  Alarm,  Electric. — »An  electric  device  de- 
signed to  give  an  alarm  and  which  is  automatically 
operated  by  a  change  of  temperature. 

Temperature  Elevation.— The  temperature  of  a  body  in 
excess  of  its  surroundings.  The  temperature  of  a 
conductor  which,  due  to  the  passage  of  a  current 
through  it,  is  greater  than  that  of  the  surrounding 
atmosphere. 

Temperature  Gradient.— A  line  which  indicates  the 
rate-of-change  in  an  object  or  mass  through  which 
heat  is  passing. 

Tempering. — Rendering  metals  hard  and  elastic  to  dif- 
ferent degrees  required  by  heating  them  to  various 
temperatures  and  then  cooling  them  suddenly. 

Temporary. — Lasting  for  a  time  only. 
Temporary  Currents. — Currents  which  continue  for  a 
short  time  only. 

Temporary  Intensity  of  Magnetization. — The  intensity 
of  magnetization  induced  for  a  short  while  in  soft 
iron  in  distinction  from  that  permanently  induced 
in  steel. 

Temporary  Magnetization. — A  term  applied  to  the  mag- 
netization induced  in  a  body  of  soft  iron  when  sub- 
jected to  the  influence  of  a  magnetic  field. 

Tenacity. — That  quality  of  bodies  which  keeps  them 
from  parting  without  considerable  force. 

Tension. — The  degree  of  stretching  to  which  a  wire, 
cord  and  the  like  is  strained  by  drawing  it  in  the 
direction  of  its  length.  Strain.  The  force  with 
which  particles  of  gas  tend  to  recede  from  each 
other  and  occupy  a  larger  space. 

Tension,  Electric. — A  term  not  properly  used,  signify- 


ELECTRICAL  DICTIONARY  279 

ing  electromotive  intensity,  electromotive  force, 
dielectric  stress  or  difference  of  potential,  all  of 
which  should  be  designated  by  their  proper  terms. 

Terminal  Pressure. — The  pressure  indicated  at  electric 
terminals. 

Terminal  Voltage. — Terminal  electromotive  force. 

Terminals. — The  poles  or  electrodes  of  a  voltaic  bat- 
tery. 

Tesla  Coil. — An  induction  coil  insulated  by  means  of 
oil. 

Tesla  Discharge. — A  disruptive  discharge  of  exceeding- 
ly high  frequency. 

Tesla  Frequencies. — Frequencies  higher  than  those 
usually  employed. 

Tesla  Transformer. — An  oil  insulated  transformer  which 
raises  the  potential  and  decreases  the  current  in 
the  secondary  and  used  by  Tesla  to  obtain  high 
frequencies. 

Test  Board. — A  board  which  is  equipped  with  spring 
jacks  or  switches  connected  with  separate  lines  to 
facilitate  the  ready  connection  of  testing  instru- 
ments with  any  particular  lines  and  employed  prin- 
cipally in  telephone  and  telegraph  central  offices. 

Test  Ring. — A  call  from  central  station  made  to  the  sub- 
scribers in  order  to  learn  whether  or  not  the  line  is 
in  good  working  condition. 

Test  Thimble. — A  thimble  provided  with  a  contact  and 
serving  in  telephone  exchanges  to  make  a  busy  test 
at  a  multiple  switchboard. 

Test  Wire  for  Multiple  Switchboard. — A  wire  making  a 
connection  with  the  jacks  of  the  same  number  of 
the  different  sections  on  a  multiple  switchboard  at 


280  ELECTRICAL  DICTIONARY 

a  central  station,  and  which  enables  the  operator 
to  ascertain  whether  a  subscriber  called  is  busy 
or  not. 

Testing. — Making  a  trial  to  determine  electric  ability. 
Determining  the  factors  of  electric  capacity  gen- 
erally in  a  circuit. 

Testing  Bank. — A  bank  employed  in  testing  circuits, 
consisting  of  lamps  or  other  resistances  and  having 
no  induction. 

Testing  Car  for  Railway  Circuits. — A  trolley  car  serv- 
ing to  make  electric  test  while  in  motion. 

Testing,  Magneto. — A  magneto-electric  machine  which 
produces  the  high  electromotive  force  necessary  to 
test  circuits  of  high  resistance. 

Testing  of  Joints. — -Ascertaining  in  any  circuit  the  usual 
insulation  or  conductor  resistance  of  a  joint. 

Testing  Room. — A  room  equipped  with  all  the  necessary 
apparatus  for  electric  testing.  A  room  on  ships 
used  for  cable  laying,  which  is  equipped  with  neces- 
sary apparatus  for  signaling  and  making  tests. 

Testing  Transformer. — A  transformer  employed  in  test- 
ing to  discover  the  efficiency  or  otherwise  of  all 
those  factors  which  enter  into  the  operation  of  an 
electric  distribution  system. 

Tetanus. — Persistent  spasm  of  the  voluntary  muscles. 
Lockjaw. 

Tetrad  Atom. — An  atom  whose  atomicity  is  four. 

Tetrivalent. — Having  an  atomicity  of  four. 

Thaumatrope. — An  optical  toy  for  showing  the  persist- 
ence of  an  impression  upon  the  eye  after  the  lumi- 
nous object  is  withdrawn,  and  consists  of  a  card 
having  on  its  opposite  faces  figures  of  two  differ- 


ELECTRICAL  DICTIONARY  281 

ent  objects,  as  a  bird  and  a  cage,  and  the  card  on 
being  rapidly  whirled  around  a  diameter  by  the 
strings  that  hold  it,  the  appearance  presented  to 
the  eye  is  that  of  a  single  picture,  as  the  bird  in  the 
cage. 

Theater  Dimmer. — A  contrivance  serving  in  theaters 
to  vary  the  intensity  of  the  light.  A  choking  coil. 

Theater  Dimming  Rheostat. — A  rheostat  used  together 
with  a  dimmer  in  a  theater. 

Theodolite. — An  instrument  variously  constructed,  used 
in  trigonometrical  surveying,  for  the  accurate 
measurement  of  horizontal  and  vertical  angles. 

Theoretical  Magnet. — An  imaginary  magnet,  assumed 
to  possess  uniform  magnetization,  infinite  length 
and  thinness.  A  hypothesis  for  the  purpose  of 
mathematical  discussion. 

Therm. — A  unit  of  heat  required  to  raise  the  tempera- 
ture of  one  gramme  of  water  one  degree,  centi- 
grade, starting  at  the  temperature  of  its  maximum 
density. 

Thermal. — Pertaining  to  heat. 

Thermal  Absorption. — The  absorption  of  heat  while  it 
is  passing  through  a  body. 

Thermal  Activity. — The  activity  which  a  body  possesses 
by  reason  of  its  heat  energy.  The  rate  at  which 
heat  is  generated.  The  rate  at  which  thermal  work 
is  done. 

Thermal  Circuit  Closer. — A  circuit  closer  whose  oper- 
ation is  effected  by  changes  of  temperature. 

Thermal  Current. — A  current  resulting  from  the  flow 
of  heat  through  a  conductor. 


282  ELECTRICAL  DICTIONARY 

Thermal  Current-Strength.— The  quantity  of  heat 
which  is  transmitted  per  second  across  a  conduct- 
or's area  of  normal  cross-section. 

Thermal  Equivalent  of  Work. — The  equivalent  of  a 
specified  quantity  of  mechanical  work  in  heat 
units. 

Thermal  Resistance. — The  resistance  which  a  body  of- 
fers to  the  passage  of  heat  through  it. 

Thermo-Barometer.-^An  instrument  by  means  of  which 
an  altitude  is  determined  by  its  reading  of  the 
boiling  temperature  of  water  at  such  altitude.  A 
hysometer. 

Thermo-Chemistry. — The  branch  of  the  science  of  chem- 
istry which  relates  to  the  measurement,  in  thermal 
units,  of  chemical  energy. 

Thermo-Electric  Call. — An  instrument  which  sounds  an 
alarm  by  means  of  electricity  when  the  tempera- 
ture goes  above  or  below  a  certain  point. 

Thermo-Electricity. — Electromotive  forces  produced 
from  heat  energy  by  direct  conversion  or  by  differ- 
ences of  temperature  at  the  junction  of  unlike 
metals. 

Thermo-Magnetic  Generator. — An  instrument  by  means 
of  which  electricity  is  produced  under  the  influence 
of  heat  and  magnetism.  A  pyro-magnetic  gener- 
ator. 

Thermometer,  Electric. — A  thermometer  whose  indica- 
tions result  from  the  variation  of  resistance  in  con- 
ductors with  variation  of  temperature.  An  instru- 
ment employed  to  ascertain  the  effects  of  an  elec- 
trical discharge,  and  which  are  determined  by  the 
movements  of  a  liquid  column,  resulting  from  the 


ELECTRICAL  DICTIONARY  283 

expansion  of  a  confined  body  of  air  which  the  dis- 
charge passes  through. 

Thermometric  Conductivity. — The  ratio  of  heat  conduc- 
tivity as  determined  by  measurement  to  the  specific 
heat  of  unit  volume. 

Thermometry. — The  science  which  treats  of  the  meas- 
urement of  temperature. 

Thermophone. — An  instrument  which  produces  sound 
by  means  of  electricity.  An  instrument  which  by 
absorbing  radiant  energy  produces  sounds. 

Thermostat. — An  apparatus  which  automatically  closes 
an  electric  circuit  when  heated,  thereby  maintain- 
ing a  specific  temperature. 

Thermostatic  Regulation. — The  regulation  of  tempera- 
ture obtained  through  the  action  of  a  thermostat. 

Third-Rail  Electric  Railway.— i&n  electric  street-car 
railway  which  employs  a  third  rail  which  is  insu- 
lated from  the  track  and  answers  for  one  side  of 
the  circuit,  while  the  outside  rails,  in  connection 
with  return  feeders,  answer  for  the  other  side  of 
the  circuit. 

Three- Coil  Armature  Winding  of  Alternator. — An  ar- 
mature winding  which  provides  for  each  and  every 
pole  in  the  field  frame,  three  coils  in  a  ring  arma- 
ture, or  three  slots  in  a  drum  armature. 

Three-Coil  Armature  Winding  of  Multiphase  Alterna- 
tor.— An  armature  winding  which  provides  for 
each  and  every  pole  in  the  field  frame,  three  coils 
in  a  ring  armature,  or  three  slots  in  a  drum  arma- 
ture, per  phase. 

Three-Part  Commutator. — A  commutator  consisting  of 
three  insulated  segments. 


284  ELECTRICAL  DICTIONARY 

Three-Phase  Armature. — An  armature  which  has  a 
three-phase  winding. 

Three-Phase  Armature  Winding. — An  armature  wind- 
ing by  which  it  is  enabled  to  produce  three-phase 
currents. 

Three-Phase  Bar- Winding  for  Armature.— A  bar  wind- 
ing for  an  armature  by  means  of  which  it  is  capable 
of  producing  three-phase  currents. 

Three-Phase  Circuit. — A  circuit  permitting  the  trans- 
mission of  three-phase  currents. 

Three-Phase  Continuous-Current  Commutating  Ma- 
chine.— A  machine  serving  to  transform  three- 
phase  alternating  currents  to  continuous  currents, 
using  a  revolving  armature  which  has  a  commuta- 
tor. 

Three-Phase  Generator. — A  generator  possessing  the 
ability  to  produce  three-phase  currents. 

Three-Phase  Motor. — A  motor  which  can  be  operated 
by  three-phase  currents. 

Three-Phase  Rotating  Magnetic  Field. — A  rotating  field 
which  a  three-phase  current  produces. 

Three-Phase  Transformer. — Three  distinct  transformers 
by  the  employment  of  which  three-phase  currents 
are  transformed. 

Three-Point  Switch. — A  switch  which  completes  a  cir- 
cuit through  three  distinct  contact  points. 

Three- Voltmeter  Method  of  Measurement. — A  method 
for  the  measurement  of  activity  in  alternating  cur- 
rent circuits  and  which  provides  for  the  employ- 
ment of  three  voltmeters  at  the  same  time. 

Three-Wire  Circuit. — A  circuit  used  in  a  three-wire  sys- 
tem. A  three-wire  diphase  or  triphase  system. 


ELECTRICAL  DICTIONARY  285 

Three-Wire  Biphase. — A  diphase  circuit  employing 
three  wires,  one  of  which  has  a  greater  area  of  cross 
section  than  the  others  and  serves,  therefore,  as  the 
common  return. 

Three-Wire  Meter. — A  meter  employed  to  record  the 
power  delivered  on  both  sides  of  a  three-wire  sys- 
tem. 

Three-Wire  Moulding. — Moulding  used  in  a  three-wire 
system  of  distribution. 

Three-Wire  Switchboard. — A  switchboard  adaptable  for 
use  in  a  three-wire  system  of  distribution. 

Three-Wire  System. — In  multiple  arc  or  constant  po- 
tential service,  a  system  of  distribution  of  electric 
current  consisting  of  three  main  wires  which  start 
at  the  generating  source  and  ramify  with  corre- 
sponding diminution  in  size  everywhere  through 
the  lighted  district;  the  dynamos  being  set  in 
groups  of  two  with  one  lateral  lead  leaving  the 
negative  binding  post  of  one  dynamo,  while  the 
positive  terminal  of  that  dynamo  connects  to  the 
negative  of  the  other,  and  the  neutral  lead  is  con- 
nected between  the  two  dynamos ;  the  other  lateral 
lead  leaving  at  the  positive  binding  post  of  the  sec- 
ond dynamo. 

Three-Wire  Transmission. — Transmission  effected  by 
the  three-wire  system. 

Three-Wire  Telephone  Switchboard. — A  branch  termi- 
nal switchboard  used  in  telephone  operations. 

Throttling. — Cutting  off  partly  or  entirely. 

Throttling  of  Lines  of  Magnetic  Force. — Any  diminu- 
tion in  magnetic  flux  density  resulting  from  a  mag- 
netic joint,  or  to  diminution  in  magnetic  permeabil- 
ity at  any  section  of  a  circuit. 


286  ELECTRICAL  DICTIONARY 

Throw. — The  deflection  of  a  needle.    Elongation. 

Throw  of  Needle. — The  angular  deflection  of  the  needle 
when  it  makes  its  first  move. 

Throw-Over  Reversing  Switch. — A  reversing  switch 
thrown  from  side  to  side  in  operating  it. 

Throw-Over  Switch. — A  switch  serving  to  quickly 
change  a  circuit  from  one  source  or  system  to  an- 
other source  or  system.  A  switch  fashioned  to  move 
about  on  an  axis,  and  which  can  be  thrown  over 
from  one  set  of  contacts  to  another. 

Thunder. — The  sound  which  follows  a  flash  of  lightning. 
The  report  of  a  discharge  of  atmospheric  electric- 
ity. 

Ticker. — An  instrument  for  receiving  stock  quotations 
and  other  information  delivered  from  the  instru- 
ment in  printing  upon  a  paper  ribbon. 

Tie  Wire. — A  wire  used  to  bind  an  insulator. 

Time-Ball,  Electric. — A  ball  which  by  means  of  electric- 
ity is  made  to  fall  from  an  elevator  position  upon  a 
high  pole ;  the  fall  occurring  exactly  at  noon  or  at 
any  preconcerted  hour,  and  intended  as  a  visual 
signal  by  which  the  correct  time  may  be  made 
known. 

Time-Detector,  Electric. — A  watchman's  clock  actuated 
by  electricity  and  which  serves  to  register  the  time 
at  which  the  watchman  visits  the  stations  on  his 
beat. 

Time-Lag  of  Magnetization. — A  condition  suggesting 
lag  between  the  moment  when  the  magnetizing  j 
force  begins  to  act  and  the  time  of  the  indicated! 
presence  of  magnetism. 

Time  of  Vibration. — The  time  necessary  for  a  back  and 


ELECTRICAL,  DICTIONARY  287 

forth  motion  of  particles  in  an  elastic  medium  to  be 
completed. 

Time^Switch. — A  switch  contrived  so  that  it  will  open 
or  close  a  circuit  at  or  after  the  expiration  of  a  cer- 
tain time.  An  automatic  switch  so  contrived  that 
a  resistance  cannot  be  inserted  into  it,  nor  can  it 
be  removed  from  a  circuit  before  the  expiration  of 
a  certain  predetermined  time. 

Tinned  Wire. — Wire  covered  with  tin  by  the  electro- 
plating process. 

Tinning  Metal. — A  solder  used  to  join  electrotype  shells 
or  for  obtaining  the  proper  condition  on  their 
backs  preparatory  to  applying  the  backing  metal. 

Toll  System. — A  system  employed  in  telephone  service 
which  provides  for  a  charge  for  each  call  made  in- 
stead of  a  specified  rate  of  rental  per  annum. 

Tone. — Sound,  or  the  character  of  sound,  or  a  sound 
considered  as  of  this  or  that  character.  A  sound 
considered  as  to  pitch. 

Toothed-Core  Armature. — An  armature  having  a  lami- 
nated core,  the  toothed  disk  of  which  has  longi- 
tudinal grooves  on  its  surface,  and  into  which  the 
armature  coils  are  placed. 

Toothed-Drum  Armature. — A  toothed-core  armature 
resembling  a  drum  in  shape. 

Toroid.. — A  solid  whose  surface  boundary  is  produced 
by  the  revolution  of  any  closed  plane  about  an  axis 
in  its  plane,  and  by  which  it  is  not  cut. 

Toroidal  Coil. — A  coil  wound  in  the  shape  of  a  toroid. 

Torque. — A  force  which  tends  to  produce  torsion  around 
an  axis,  as  in  the  pulling  or  turning  moment  of  an 
electric  motor's  armature  upon  its  shaft.  The  mo- 


288  ELECTRICAL  DICTIONARY 

ment  of  force  which  causes  the  rotation  of  a  dyna- 
mo or  other  machine  when  applied  to  it.  The  me- 
chanical, turning  or  rotary  force  whose  action  pro- 
duces the  rotation  of  the  armature  of  a  dynamo 
electric  machine  or  motor.  The  ratio,  at  belt  or 
pulley,  of  a  motor's  mechanical  activity  to  the  an- 
gular velocity. 

Torque  Efficiency. — The  relation  of  the  torque  which  a 
motor  exerts  at  a  specific  terminal  activity,  to  that 
which  would  be  exerted  were  there  no  loss  of  en- 
ergy. 

Torreicellian  Vacuum. — The  vacuum  which  exists  above 
the  mercury  column  in  the  tube  of  a  barometer; 
the  principle  of  this  vacuum  being  applied  in  the 
Geissler  and  other  air  pumps. 

Torsion. — The  twisting  or  wrenching  of  a  body  by  the 
exertion  of  a  lateral  force. 

Total  Candle-Power. — The  total  light  given  out  by  any 
luminous  source. 

Total  Resistance. — The  total  of  a  circuit's  resistance. 

Tower-System  of  Electric  Lighting". — The  employment 
of  high  towers  for  lighting  large  areas;  the  lights 
being  placed  at  the  top  of  the  towers. 

Tower  Wagon. — -A  wagon  equipped  with  a  skeleton 
tower  and  tools  and  employed  in  repair  work  on 
trolley  lines;  the  wires  being  easily  reached  by 
means  of  the  tower. 

Track  Bond. — Rail  bond. 

Traction,  Electric. — The  driving  of  a  car  on  any  convey- 
ance by  means  of  an  electric  motor. 

Train  Describer. — An  electrical  instrument  which  indi- 
cates automatically  from  a  distance  the  location 


ELECTRICAL  DICTIONARY  289 

«* 

and  character  of  railroad  trains  when  out  on  the 
line. 

Train  Wire. — A  wire  connected  with  the  chief  train  dis- 
patcher's office  and  used  in  the  block  system  of 
railroading  for  transmitting  train  orders  only. 

Trajectory. — /The  curve  described  by  a  body  thrown  up- 
ward obliquely  in  the  air.  A  curve,  which  pursuant 
to  a  given  law,  cuts  a  system  of  curves  produced  by 
varying  a  parameter. 

Trans- Continental  Telephony. — Communication  across 
the  continent  by  telephone. 

Transfer  Bus-Bar. — A  bus-bar  whose  employment 
serves  to  obviate  a  sudden  variation  of  potential 
by  gradually  transferring  a  feeder  from  one  bus- 
bar to  another  instead  of  throwing  it  over  directly. 

Transform. — To  convert.  To  change.  To  change  a 
primary  current  with  high  initial  electromotive 
force  into  a  secondary  current  with  low  initial  elec- 
tromotive force.  To  change  an  alternating  current 
into  a  continuous  current. 

Transformation  of  Electromotive  Force  or  Current. — 

The  conversion  of  electric  energy  into  another  form 
of  energy. 

Transformation  of  Heat.— The  conversion  of  heat  en- 
ergy into  another  form  of  energy. 

Transformer. — An  induction  coil  by  which  a  primary 
current  of  high  initial  electromotive  force  is  made 
to  produce  a  secondary  current  of  low  initial  elec- 
tromotive force. 

Transformer  Fuse. — A  fuse  used  in  either  a  transform- 
er's primary  or  secondary  circuit. 


290  ELECTRICAL  DICTIONARY 

Transformer  Fuse-Block. — A  fuse-block  inside  of  or 
contiguous  to  a  transformer  case. 

Transformer  Guard. — A  lightning  guard  used  in  con- 
nection with  a  transformer.  A  contrivance  serving 
to  ground  the  secondary  of  a  transformer  in  the 
event  of  its  making  accidental  contact  with  the 
primary. 

Transformer  Lightning-Arrester. — A  style  of  lightning 
arrester  serving  to  protect  transformers. 

Transformer  Motor. — An  induction  motor. 

Transformer  Stampings. — Stampings  made  from  sheet 
steel  and  used  to  build  the  laminated  cores  of  trans- 
formers. 

Transformer  Sub-Station. — A  sub-station  serving  as  a 
sub-center  of  distribution  and  containing  trans- 
formers in  groups. 

Transforming. — Converting  high  initial  electromotive 
force  into  low  initial  electromotive  force.  Convert- 
ing electric  energy  from  lower  pressure  and  strong- 
er current  to  higher  pressure  and  weaker  current. 

rransforming  Currents. — Effecting  a  change  in  the 
value  of  a  circuit's  current  strength  with  a  corre- 
sponding opposite  change  of  pressure. 

Transforming  Down. — Reducing  the  pressure  in  a  cir- 
cuit of  distribution  by  the  use  of  a  step-down  trans- 
former. 

Transforming  Station. — Sub-station  containing  a  num- 
ber of  transformers  which  serve  to  supply  a  collec- 
tion of  buildings  in  that  location. 

Transforming  Up. — Increasing  the  pressure  in  a  circuit 
of  distribution  by  the  use  of  a  step-up  transformer. 

Translucence. — Partial     transparency.       Transmitting 


ELECTRICAL  DICTIONARY  291 

light,  but  not  permitting  objects  to  be  distinctly 
seen. 

Translucent-Disc  Photometer. — -A  photometer  in  which 
the  two  lights  to  be  compared  are  at  or  opposite 
to  the  ends  of  a  bar  scale,  with  a  partly  translucent 
and  partly  opaque  disc  between  them ;  the  intensity 
of  the  light  is  then  determined  by  the  distance  of 
the  lights  from  the  disc  when  both  of  its  surfaces 
show  an  equal  illumination. 

Transmission  Dynamometer. — A  dynamometer  which 
measures  and  transmits  the  power  to  some  machine 
in  distinction  from  one  which  absorbs  the  energy 
it  measures. 

Transmission,   Electric. — The   transmission    of   energy 

by  electric  currents  from  one  point  to  another. 
Transmission  of  Energy. — The  transmission  of  energy 

from  one  point  to  another. 
Transmission  of  Electric  Energy. — The  transmission  of 

electric  energy  from  one  point  to  another. 
Transmitted    Power. — Power    transmitted    from    one 

point  to  another. 

Transmitter,  Electric. — A  term  embracing  in  its  sig- 
nificance the  entire  apparatus  employed  in  tele- 
graph or  telephone  systems  for  the  transmission  of 
electric  impulses  over  a  line  wire  or  conductor. 

Transposing. — A  method  for  laying  metallic  circuits, 
serving  in  a  telephone  system  to  obviate  the  dele- 
terious effects  of  mutual  induction,  and  effected  by 
crossing  equal  lengths  of  consecutive  sections  of 
the  line  alternately. 

Transverse  Vibration. — A  vibration  in  which  the  motion 
of  the  successive  particles  in  an  elastic  medium  is 


292  ELECTRICAL  DICTIONARY 

at  right  angles  to  the  progressive  movement  of  the 
wave  through  the  medium. 

Travelling  Derrick. — A  derrick  erected  on  a  platform 
and  arranged  to  move  on  guide  rails,  thus  ena- 
bling it  to  shift  and  move  heavy  bodies  through 
short  distances. 

Travelling  Motor. — A  motor  mounted  on  a  movable  car 
in  distinction  from  a  stationary  motor. 

Travelling  of  Arc. — The  inconstancy  of  brilliancy  in 
a  carbon  arc  resulting  from  a  shifting  of  the  posi- 
tion of  the  arc  between  the  electrodes. 

Traversing  Motor,  Electric. — A  motor  operating  with 
a  regular  to-and-fro  movement  through  a  circum- 
scribed distance.  The  motor  which  operates  the 
traverse  in  a  crane  worked  by  electricity. 

Treated  Coke  Filament. — A  coke  filament  for  incan- 
descent lamps  which  has  beeen  treated  by  the  flash- 
ing process. 

Tree-System  of  Parallel  Distribution. — A  system  of 
incandescent  lamp  parallel  distribution  which  may 
be  described  by  comparing  the  main  conductors  to 
the  trunk  of  a  tree,  and  the  auxiliary  leads,  which 
run  in  various  directions,  to  the  branches;  the 
lamps  occupying  the  position  of  the  leaves  and 
twigs. 

Trega. — A  prefix  meaning  a  trillion. 
Tregohm. — One   trillion   ohms. 

Trevelyan  Effect. — A  musical  sound  which  under 
certain  conditions  is  emitted  when  a  body  of 
heated  copper  is  placed  on  thin  edges  supported 
on  a  block  of  cold  lead. 


ELECTRICAL  DICTIONARY  293 

Triangular  Triphase  Winding. — Three-wire  triphase 
or  interlinking. 

Tricro. — A  prefix  meaning  one  trillionth  part. 

Tricro-Ampere. — The  one  trillionth  of  an  ampere. 

Tricrohm. — The  one  trillionth  of  an  ohm. 

Trigonometrical. — Pertaining  to  trigonometry.  Per- 
taining to  the  science  of  angles. 

Trigonometrical  Functions. — Quantities  definitely  re- 
lated to  angles  taken  as  independed  variables. 

Triphase. — Three-phase. 

Triphase  Alternating  Currents. — Three  monophase 
alternating  currents,  the  phases  of  which  are  dis- 
placed, with  respect  to  one  another,  by  one-third 
of  a  cycle. 

Triple-Pole  Single-Throw  Switch. — A  single-throw 
switch  provided  with  three  blades  and  designed  to 
close  three  circuits  at  one  and  the  same  time. 

Triply  Re-Entrant  Armature  Winding. — An  armature 
winding  having  three  distinct  windings,  each  one 
being  separately  re-entrant. 

Trolley. — A  contact-wheel  which  rolls  over  the  supply 
wire  in  a  trolley  line  and  takes  off  the  current  re- 
quired to  operate  the  motor  cars. 

Trolley  Base. — A  base  serving  to  support  a  trolley  pole 
and  which  is  equipped  with  springs  in  order  to 
maintain  a  steady  contact  between  the  trolley  and 
the  trolley  wire;  a  swivel  joint  being,  in  addition 
provided  for  reversing  the  direction  of  the  trolley 
pole. 

Trolley  Bus-Bar. — A  bus-bar  in  a  railway  power  station 
which  is  connected  with  the  trolley  system  in  dis- 
tinction to  one  which  is  connected  with  the  ground. 


294  ELECTRICAL  DICTIONARY 

Trolley  Car. — A  motor  car  in  an  electric  railroad  trolley 
system. 

Trolley  Car-Controller.— A  series-parallel  car-control- 
ler. 

Trolley-Crossing. — An  insulating  contrivance,  serving 
at  the  crossing  of  two  trolley  wires,  to  enable  a 
trolley  wheel  running  on  one  line,  to  cross  the 
other  without  making  electrical  contact.  A  plate 
with  guides,  provided  at  the  crossing  of  two  trol- 
ley wires,  to  aid  the  trolley  wheel  in  crossing. 

Trolley  Wheel. — A  metallic  wheel  fixed  to  the  upper 
end  of  the  trolley  pole,  and  which  rolls  over  the 
trolley  wire,  taking  therefrom  the  current  required 
to  operate  the  motor. 

Trolley  Wire. — The  overhead  supply  wire  in  a  trolley 
system  from  which  the  current  required  to  operate 
the  motor  is  taken  by  the  trolley  wheel. 

Trolley  Wire  Splice. — A  splice  used  in  joining  the  ends 
of  trolley  wires  and  effected  by  inserting  the  ends 
of  the  two  wires  into  a  tubular  conductor  and  then 
brazing  them. 

True  Resistance. — The  true  resistance  measured  in 
ohms  in  distinction  from  counter  electro-motive 
force.  The  resistance  offered  by  a  conductor  to 
the  passage  of  a  current  by  reason  of  the  area  of 
cross  section  and  resistivity. 

Trumpet,  Electric. — An  instrument  which  has  a  vibrat- 
ing tongue  and  which  is  actuated  by  electricity,  as 
the  buzzer,  and  adjusted  in  the  small  end  of  a  tube 
of  trumpet  shape. 

Trunnion  Screws. — A  pair  of  screws  the  opposite  points 
of  which  constitute  the  pivots  of  a  movable  shutter, 
armature  or  other  revolving  device. 


ELECTRICAL  DICTIONARY  295 

Trunk  Call. — A  telephone  call  made  through  a  trunk 
line. 

Trunk  Connection. — A  connection  set  up  through  a 
telephone  trunk  wire. 

Trunk-Line  Wire. — Wires  running  through  between 
stations  remote  from  each  other,  their  ends  only 
being  provided  with  transmitting  and  receiving 
instruments.  Main  line  telephone  wires  which 
serve  to  connect  two  terminal  offices  for  connec- 
tion to  sub-offices  or  subscribers.  A  main  line  tele- 
phone wire  serving  to  connect  two  important  ter- 
minals. 

Trunk  Wire. — A  trunk  line  or  main  telephone  wire.  A 
connecting  wire  extending  from  place  to  place,  or 
exchange  to  exchange,  in  distinction  from  a  per- 
manently connected  subscriber's  wire. 

Tubular  Electro-Magnet. — An  electro-magnet  resem- 
bling a  tube  in  shape. 

Tubular  Magnet. — A  magnet  with  a  cylindrical  casing 
of  iron  connected  at  one  end  to  the  core.  An  iron- 
clad magnet. 

Tumbling  Box. — A  box  devised  to  rotate  and  employed 
to  polish  metallic  articles  preparatory  to  electro- 
plating, and  which  is  effected  by  the  attrition  of 
the  objects  against  one  another,  in  the  box,  while 
the  same  is  rotating. 

Tuning  of  Electric  Circuit. — Changing  a  circuit's  period 
or  varying  either  the  self-induction  or  capacity  of 
it  in  order  that  it  may  be  brought  into  resonance 
with  another  circuit. 

Tunnel  Armature. — An  armature  of  a  dynamo-electric 


296  ELECTRICAL  DICTIONARY 

machine,  with  holes  beneath  the  outer  surface  of 
the  core,  into  which  the  conductors  are  placed. 
Turnbuckle. — A  device  employed  to  strain  span  wires. 
v  A  rod,  guy,  or  line  screw  tightener. 

Twist  System. — A  method  of  twisting  overhead  wires 
into  a  form  of  helical  twist,  as  they  are  being  run, 
in  order  to  destroy  mutual  inductive  disturbances. 

Twist  in  Armature  Leads. — A  displacement  made  of  the 
terminals  of  the  armature  leading  wires,  which  are 
connected  with  the  segments  of  the  commutator, 
as  referred  to  the  position  of  the  armature  coils,  in 
order  that  a  better  position  for  the  diameter  of 
commutation  may  be  obtained,  and  accordingly 
for  the  points  of  contact  of  the  commutator's  col- 
lecting brushes. 

Twisted  Strip-Voltmeter. — A  voltmeter  which  consists 
of  a  strip  of  platinum-silver,  twisted,  and  whose 
operation  is  effected  by  the  coiling  and  uncoiling 
of  the  strip,  due  to  variations  in  its  temperature, 
produced  by  the  passage  through  it  of  the  current 
to  be  measured. 

Twisting  Force. — Torque. 

Two-Circuit  Armature-Winding. — An  armature  wind- 
ing which,  notwithstanding  how  great  may  be  the 
number  of  poles,  provides  only  two  circuits 
through  an  armature  between  the  commutator 
brushes. 

Two-Circuit  Single-Wound  Armature. — An  armature 
whose  pitch  is  always  forward,  and  which  possesses 
two  circuits  regardless  of  the  number  of  poles. 

Two-Layer  Armature- Winding. — An  armature  winding 
applied  in  two  layers.  A  winding  possessing  more 


ELECTRICAL  DICTIONARY  297 

than  two  layers,  but  which  would  admit  of  appli- 
cation in  two  layers  only. 

Two-Phase  Circuit. — A  diphase  circuit. 

Two-Phase  Dynamo  or  Generator. — A  diphase  gene- 
rator. 

Two-Phase  Motor. — A  diphase  motor. 

Two-Phase  Rotary-Transformer. — A  diphase  rotary 
transformer. 

Two-Wire  Incandescent  Lighting. — In  a  system  of  in- 
candescent lighting,  the  employment  of  a  single 
pair  of  mains,  in  distinction  from  three-wire  in- 
candescent lighting. 

Two-Wire  Moulding. — A  moulding  having  two  chan- 
nels or  grooves  and  serving  to  receive  two-wire 
mains  or  branches. 

Two-Wire  Multiple-Switchboard. — A  multiple  tele- 
phone switchboard  which  has  the  jacks  of  a  sub- 
scriber's circuit  connected  by  two  wires. 


U. 

Ultra-Gaseous  Matter. — Gas  rarefied  to  such  a  high  de- 
gree that  its  molecules  do  not  collide.  Radiant 
matter. 

Ultra-Incandescent  Lamp. — An  incandescent  lamp 
whose  light  is  increased  in  intensity  by  the  radia- 
tive powers  of  oxides  of  thorium,  etc.,  with  which 
the  filament  is  covered. 

Ultra-Ultra- Violet. — A  term  for  luminous  frequencies 
greatly  beyond  the  violet  in  the  spectrum. 

Ultra- Violet  Rays. — A  term  for  rays  the  frequencies  of 
which  exceed  those  of  violet  light. 


ELECTRICAL  DICTIONARY 

Ultra- Violet  Spectrum.— That  part  of  the  spectrum  ly- 
ing beyond  the  violet,  or  that  part,  the  frequencies 
of  which  exceed  those  of  the  violet. 

Unbalanced  Load. — A  load  whose  distribution  is  not 
symmetrical. 

Unbalanced  Polyphase  System. — A  multiphase  system 
wherein  the  distribution  of  the  load  and,  conse- 
quently, the  pressures  and  currents  are  unsymmet- 
rically  distributed. 

Unbuilding  of  Dynamo.— The  loss  of  its  charge  or  ex- 
citation by  a  self-exciting  dynamo. 

Underground-Cable  Terminal. — The  point  at  which  an 
underground  cable  comes  out  of  the  ground.  A 
distributing  board  located  at  the  point  where  an 
underground  cable  goes  into  or  emerges  from  the 
ground,  for  the  purpose  of  conveniently  making 
and  changing  the  connections. 

Underground  Conductor. — An  electric  conductor  insu- 
lated and  placed  under  the  surface  of  the  earth 
and  passing  through  the  ground  proper  or  through 
conduits. 

Underground  Electric  Conduit. — A  subway  for  the  re- 
ception of  electric  telegraph  and  other  conductors 
under  the  surface,  usually  in  the  line  of  streets,  to 
dispense  with  telegraph  poles  and  aerial  wiring. 

Underground  Trolley  System. — An  electric  trolley 
system  in  which  a  plow  or  sled  is  substituted  for 
the  trolley  wheel  and  is  drawn  after  or  pushed 
ahead  of  the  car,  thus  making  a  contact  with  a 
wire  running  inside  of  a  slotted  underground  con- 
duit. 

Undulating  Current. — An  undulatory  current.    A  cur- 


ELECTRICAL  DICTIONARY  299 

rent    whose    direction    is    constant,    but    whose 
strength  is  continuously  varying. 

Undulator. — A  type  of  rotating  commutator  employed 
on  continuous-current  circuits  for  the  use  of  trans- 
formers. A  commutating  device  which,  from  a 
continuous-current  circuit,  operates  an  alternating- 
current  apparatus. 

Undulatory  Currents. — Currents  which  change  in 
strength  without  any  sudden  transition  from  ac- 
tion to  inaction,  as  in  the  make  and  break  current. 

Undulatory  Discharge. — A  discharge  the  strength  of 
which  changes  gradually  without  any  change  of 
direction. 

Undulatory  Winding. — A  wave  winding. 

Uni-Directed  Currents. — Currents  which,  by  means  of 
a  commutator,  have  been  made  to  take  the  same 
direction. 

Uni-Directional. — Having  the  same  direction. 

Uni-Directional     Discharge. — An     electric     discharge 

whk-h  follows  t.hfi  same  direction  from  first  to  last. 

Uniform  Density  of  Field. — A  field  in  which  all  equal 
areas  of  similar  cross  section  have  the  same  den- 
sity. 

Uniform  Flux. — Uniform  magnetic  flux. 

Uniform  Magnetic  Field. — A  field  of  uniform  strength 
in  all  portions — as  instance  the  magnetic  field  of 
the  earth — -and  when  artificially  obtained,  which 
cannot  be  definitely  done,  it  implies  great  cross  section 
of  magnet  pole  in  proportion  to  the  length  of  the 


300 


ELECTRICAL  DICTIONARY 


magnetic  needle  which  it  affects  and  which  serves 
to  ascertain  its  uniformity. 

Uniform  Magnetic  Flux.  —  A  magnetic  flux  the  density 
of  which  is  uniform. 

Uniform  Magnetization.  —  Such  character  of  magnetiza- 
tion of  a  bar  of  iron  that  the  same  quantity  of 
magnetic  flux  will  traverse  equal  areas  of  normal 
cross-section. 

Uniform  Potential.  —  A  potential  whose  value  is  in- 
variable. 

Uniformly  Distributed  Current.—  A  steady  current,  A 
current  whose  density  in  a  cross-section  of  a  con- 
ductor is  the  same  at  all  points. 

Uniphase.  —  A  single  phase.    Monophase. 

Uniphase  Alternator.  —  An    alternator   which  produces 

single-phase  currents. 
Unipolar.  —  Having  one  pole  only. 

Unipolar  Armature.  —  An  armature  whose  windings 
continuously  cut  the  lines  of  force  about  the  one 
pole,  its  polarity,  in  consequence,  being  unchanged 
in  its  rotation. 

Unipolar  Dynamo.  —  A  dynamo  equipped  with  a  uni- 
polar armature.  •  A  dynamo  so  constructed  that  one 
portion  of  the  conductor  slides  on  or  around  the 
magnet  in  consequence  of  which  it  cuts  lines  of 
force  always  near  the  same  pole  of  the  magnet.  A 
dynamo  with  one  field  magnet. 

Unipolar  Magnet.  —  A  proposed  term  for  a  poised  or 
suspended  magnet  one  of  whose  poles  lies  in  the 
axis  of  suspension. 

Unit  of  Acceleration.  —  An  acceleration  which  imparts 


ELECTRICAL  DICTIONARY  301 

unit  velocity  in  unit  time  to  a  body ;  for  instance : 
the  centimetre-second. 

Unit  of  Activity. — A  rate-of-doing  work  equal  to  one 
unit  of  work  in  each  second.  An  activity  of  one 
erg  per  second  in  the  C.  G.  S.  system  and  the  Watt 
in  the  practical  system. 

Unit  of  Electric  Quantity. — The  coulomb  in  the  unit 
practical  system.  A  quantity  of  electricity  trans- 
mitted by  a  unit  of  current  per  second. 

Unit  of  Electric  Supply. — A  unit  whose  value  would 
be  represented  by  the  flowing  for  one  hour  of  one 
thousand  amperes  under  an  electro-motive  force 
of  one  volt  and  which  was  adopted  for  present 
needs  by  the  Board  of  Trade  in  England.  Electric 
energy  equal  to  3,600,000  joules.  One  Kilowatt- 
hour. 

Unit  of  Electric  Work.— The  joule. 

Unit  of  Electrostatic  Capacity. — That  capacity  of  a  con- 
ductor or  condenser  which  admits  of  its  being 
charged  with  a  quantity  of  electricity  equal  to 
one  coulomb  by  an  electro-motive  force  of  one  volt. 

Unit  of  Force. — The  fundamental  or  C.  G.  S.  unit  of 
force,  which  is  the  dyne.  A  force  which  can  im- 
part an  acceleration  of  one  centimetre-per-second 
to  a  mass  of  one  gramme  per  second. 

Unit  of  Heat. — The  British  unit  of  heat  or  the  pound- 
degree  Fahrenheit,  which  is  the  quantity  of  heat 
required  to  raise  the  temperature  of  a  pound  of 
water  from  32  deg.  to  33  deg.  Fahr.  The  C.  G.  S. 
unit  is  the  gramme-degree  centigrade;  another 
metric  unit  is  the  kilogramme  centigrade;  the  lat- 
ter being  termed  the  calorie,  and  the  former  the 


302  ELECTRICAL  DICTIONARY 

joule;  the  term  joule  being  applied  to  a  quantity 
of  heat  equivalent  to  the  energy  of  a  Watt-second 
or  volt-coulomb;  equal  to  .241  gramme-degree 
calorie. 

Unit  of  Illumination. — The  lux. 

Unit  of  Magnetic  Flux. — The  quantity  of  flux  which 
will  pass  through  a  magnetic  circuit  the  reluctance 
of  which  is  one  oersted,  under  a  magneto-motive 
force  of  one  gilbert. 

Unit  of  Magnetic  Intensity. — The  intensity  of  a  field 
of  108  C.  G.  S.  The  gauss. 

Unit  of  Magneto-Motive  Force. — A  force  equal  to  0.7958 
ampere-hour.  The  gilbert.  That  magneto-motive 
force  which  is  necessary  to  cause  one  unit  of  flux 
to  pass  through  a  circuit  against  a  magnetic  re- 
sistance of  an  oersted. 

Unit  of  Output  of  Dynamo-Electric  Machine. — The  unit 
of  electric  force  supplied  by  the  current  of  a 
dynamo-electric  machine.  The  kilowatt. 

Unit  of  Photometric  Intensity. — The  intensity  of  light 
that  a  candle  which  consumes  2  grains  of  sperm 
wax  per  minute  will  produce;  the  candle  being  of 
specified  composition  and  dimensions. 

Unit  of  Resistance. — The  original  ohm,  so  termed  pre- 
.  vious  to  1884.     A  resistance  which  requires  unit 
difference  of  potential  to  cause  the  passage  of  unit 
current  strength  through  it. 

Unit  Strength  of  Current. — The  ampere  in  the  practical 
system  of  units  and  ten  amperes  in  the  C.  G.  S. 
system  of  units.  A  strength  of  current  which  will 
exert  a  force  of  one  dyne  on  a  unit  magnetic  pole 
when  the  current  is  passed  through  a  circuit  one 


ELECTRICAL  DICTIONARY  303 

centimetre  in  length  arranged  in  an  arc  of  a  circle 
one  centimetre  in  radius,  the  pole  being  placed  in 
the  center  of  the  arc. 

Units  of  Work. — The  unit  of  energy  or  the  erg,  the  cor- 
relative of  which  is  work  and  which  is  opposite  to 
and  equal  to  the  energy  expended  in  its  accomplish- 
ment. 

Universal  Ether. — The  ether  supposed  to  exist  every- 
where in  space. 

Unmarked  End  of  Magnet. — A  term  by  which  the  south- 
seeking  pole  of  the  magnet  was  once  known. 

Unmarked  Pole  of  Magnet. — A  magnet's  south-seeking 
pole. 

Unmarked  Magnet  Pole. — A  name  signifying  a  mag- 
net's south  pole. 

Unvarying  Current. — A  current  whose  strength  does 
not  vary. 

Uranium  Rays. — Becquerel  rays. 

Useful  Life  of  Incandescent  Lamp. — The  length  of  time 
during  which  an  incandescent  lamp  performs  effi- 
cient duty. 

V. 

Vacuum. — A  space  empty  or  void  of  all  matter.  A 
space  from  which  all  gas  has  been  exhausted. 

Vacuum  Pump. — An  air  pump. 

Vacuum-Tube  Lighting. — Illumination  artificially  ob- 
tained by  passing  electric  charges  through  vacuum 
tubes. 

Vacuum  Tubes. — Tubes  of  glass  through  which  electric 
discharges  are  passed  after  the  gases  have  been 


304  ELECTRICAL  DICTIONARY 

partially  removed,  thereby  obtaining  luminous  ef- 
fects— Koentgen's,  Crookes'  and  other  high  vac- 
uum tubes. 

Valency. — The  relative  power  of  replacing  hydrogen 
or  combining  therewith,  possessed  by  different  ele- 
ments. 

Vapor. — Any  substance  in  the  gaseous  or  aeriform  state 
the  condition  of  which  is  ordinarily  that  of  a  liquid 
or  solid. 

Vapor  Globe  of  Incandescent  Lamp. — A  glass  globe  by 
which  the  chamber  of  an  incandescent  lamp  is  sur- 
rounded, which  enables  the  lamp  to  be  used  in 
places  where  it  is  exposed  to  water  or  to  be  used 
in  an  explosive  atmosphere. 

Vapor  Pressure. — The  pressure  at  which  liquids  va- 
porize. 

Vaporization. — The  act  of  vaporizing  or  the  state  of 
being  converted  into  vapor.  The  artificial  forma- 
tion of  vapor. 

Variable  Resistance. — A  resistance  whose  value  is  capa- 
ble of  being  varied  or  changed.  Adjustable  re- 
sistance. 

Variation  of  Declination. — A  variation,  at  any  place, 
of  the  earth's  magnetic  declination. 

Variometer. — An  instrument  employed  to  determine 
the  relative  values  of  the  horizontal  component  of 
the  earth's  magnetic  field  in  different  places. 

Var ley's  Photometer. — A  style  of  photometer  which  de- 
termines the  intensity  of  the  light  to  be  measured 
from  the  relative  openings  of  two  concentric  cir- 
cular diaphragms  introduced  into  two  discs  which 


ELECTRICAL  DICTIONARY  305 

revolve ;  the  standard  light  and  that  which  is  to 
be  measured,  passing  respectively  through  them. 

Vector. — A  quantity  which  has  both  magnitude  and 
direction. 

Vector  Diagram. — A  diagram  which  shows  the  relations 
of  vector  quantities. 

Vector  Equations. — Equations  which  connect  vector 
quantities. 

Vector  Potential. — A  potential  which  has  both  magni- 
tude and  direction. 

Velocity. — Rate  of  motion.  The  relation  of  motion  to 
time,  measured  by  the  number  of  units  of  space 
passed  over  by  the  moving  body  in  a  unit  of  time ; 
usually  the  number  of  feet  in  a  second. 

Velocity  of  Discharge. — The  velocity  of  an  escaping 
gas  or  liquid  from  an  opening  in  a  specified  time. 
The  time  consumed  by  a  discharge  in  passing  from 
a  specified  length  of  conductor. 

Velocity  Ratio. — A  term  applied  to  the  ratios  existing 
between  the  electrostatic  and  electro-magnetic 
units.  The  relation  between  the  velocities  of  two 
reciprocal  parts  of  a  machine. 

Ventilated  Armature- Windings. — Armature  windings 
so  constructed  as  to  be  readily  cooled  by  driving 
currents  of  air  over  them. 

Ventilation  of  Armature  of  Dynamo  or  Motor. — Ven- 
tilation of  the  armature  by  means  of  air  supplied 
through  apertures  in  it  and  which  is  provided  for 
in  order  to  obviate  too  great  a  rise  in  temperature 
during  the  operation  of  the  machine. 

Vernier. — A  short  scale  made  to  slide  along  the  divi- 
sions of  a  graduated  instrument  for  indicating 


306  ELECTRICAL  DICTIONARY 

parts  of  divisions,  as  the  limb  of  a  sextant  or  the 
scale  of  a  barometer. 

Vernier  Caliper. — A  vernier  provided  with  a  vernier 
scale  to  insure  greater  exactness  in  observation. 

Vernier  Wire-Gauge. — A  micrometer  wire  gauge. 

Vibrating  Contact. — A  spring  contact  which  automati- 
cally opens  and  closes  a  circuit  by  being  connected 
with  one  part  of  the  circuit  in  such  manner  as  to 
enable  it  to  vibrate  towards  and  from  another  part 
of  the  circuit. 

Vibration. — Quick  motion  to  and  fro.  Oscillation  as  of 
a  pendulum  or  musical  cord. 

Vibration  Frequency. — The  number  of  vibrations  per 
second. 

Virgin  Iron. — Iron  which  has  never  been  magnetized. 

Viscous  Hysteresis. — The  creeping  up  by  degrees  of 
magnetization  upon  the  application  of  a  magnetic 
force  with  positive  steadiness  to  a  bar  of  iron,  and 
which  may  equal  several  per  -cent  of  the  total  mag- 
netization, and  continue  in  effect  for  half  hour  or 
so.  The  true  magnetic  lag. 

Vis- Viva. — The  kinetic  energy  of  a  moving  body.  Me- 
chanical energy. 

Vitreous. — Pertaining  to  glass. 

Volatilization  Electric. — The  superficial  sublimation  or 
evaporation  of  a  substance  under  the  influence  of 
negative  electricity. 

Volt. — The  practical  unit  of  electro-motive  force  or 
difference  of  potential.  An  electro-motive  force 
which  would  cause  a  current  of  one  ampere  to  flow 
through  a  resistance  of  one  ohm.  The  electro- 
motive force  induced  in  a  conductor  by  its  cutting 


ELECTRICAL  DICTIONARY  307 

100,000,000  lines  of  force  per  second.  Such  a  rise 
of  potential  as  would  be  produced  by  charging  a 
condenser  of  one  farad  capacity  with  one  coulomb. 
An  electro-motive  force  equal  to  10s  absolute  elec- 
tro-magnetic units,  or  to  the  one-three-hundredth 
electrostatic  unit. 

Volt-Ammeter. — A  term  applied  to  an  instrument  which 
can  measure  either  or  both  volts  and  amperes  in 
a  circuit. 

Volt-Ampere.— The  watt. 

Voltage. — -Potential  difference  or  electro-motive  force 
expressed  in  volts. 

Voltaic  Arc. — The  brilliant  arc  between  two  carbon 
electrodes  barely  separated,  caused  by  a  current  of 
adequate  strength  and  involving  adequate  poten- 
tial difference;  the  pencils  of  carbon  forming  ter- 
minals in  the  circuit;  being  first  placed  in  contact 
and  then  slightly  separated. 

Voltaic  Cell. — Two  metals  or  a  metal  and  a  metalloid 
which  when  combined  and  immersed  in  electrolytes 
and  connected  by  a  conductor  will  generate  elec- 
tricity. 

Voltaic  Effect. — The  potential  difference  developed  by 
contact  of  unlike  conducting  metals. 

Voltameter. — An  apparatus  employed  to  determine  the 
quantity  of  electricity  flowing  through  a  conduc- 
tor by  measuring  its  electrolytic  action. 

Vulcabeston. — An  insulating  material  composed  of  rub- 
ber and  asbestos. 

Vulcanite. — Vulcanized  india  rubber,  valuable  for  its 
high  insulating  properties  and  specific  inductive 
capability. 


308  ELECTRICAL  DICTIONARY 

Vulcanized  Fibre. — An  insulating  material  used  where 

the  highest  insulation  is  required. 
Vulcanizing  Wooden  Poles. — Confining  wooden  poles  in 

a  tight  cylinder  and  then  subjecting  them  to  the 

action  of  heat. 

W. 

Wall  Bracket. — An  insulator  bracket  fastened  to  the 
wall. 

Wall  Set. — Telephone  apparatus  set  against  a  wall. 

Wall  Socket. — A  socket  for  an  incandescent  lamp  de- 
signed to  be  attached  to  a  wall. 

Wandering  of  Electric  Spark. — A  brilliant  globule  pro- 
duced by  a  discharge,  and  which  moves  in  a  slow 
and  irregular  manner  over  the  surface  of  the  tin 
foil  in  a  condenser  to  which  the  terminals  of  a 
rheostatic  machine  are  placed,  when  a  perforation 
accidentally  happens  to  the  mica  plate  in  the  con- 
denser. 

Waste  Magnetic  Field. — A  stray  field. 

Watch-Case  Telephone  Receiver. — A  small  telephone 
receiver  resembling  a  watch  case. 

Watchman's  Electric  Register. — A  style  of  recorder 
which  makes  a  permanent  record  of  the  visits  of 
a  watchman  to  the  different  portions  of  his  beat 
at  stated  intervals. 

Water-Cooled  Transformer. — A  transformer  cooled  by 
means  of  water  being  forced  through  or  around  it. 

Water  Horse-Power. — A  horse  power  which  falling 
water  develops  and  equal  to  about  15  cubic  feet 
of  water  falling  through  a  distance  of  one  foot  per 
second. 


ELECTRICAL  DICTIONARY  309 

Water-Level  Alarm,  Electric. — An  electrically  sounded 

alarm  when  a  change  of  water  level  takes  place  in 

a  tank  or  boiler. 
Water-Pipe  Resistance. — A  resistance  offered  by  any 

pipe  to  the  water  flowing  through  it. 
Water-Proof  Wire. — Wire  encased  in  water-proof  covr 

ering. 

Water  Pyrometer. — A  pyrometer  which  determines  the 
temperature  of  a  furnace  or  other  source  of  in- 
tense heat  by  exposing  a  metal  cylinder  of  a  speci- 
fied weight  to  the  source  of  heat  for  a  specified 
time  and  then  placing  the  cylinder  into  a  known 
weight  of  water  and  noting  the  increase  of  tem- 
perature in  the  water. 

Water  Rheostat. — A  rheostat  the  resistance  of  which  is 
determined  by  means  of  a  quantity  of  water  of 
fixed  dimensions. 

Watt. — The  practical  unit  of  electric  activity,  rate  of 
work  or  rate  of  energy.  The  power  is  equivalent 
to  44.25  foot-pounds  of  work  done  in  a  minute,  or 
0.7375  foot-pound  of  work  done  in  a  second. 

Watt  Arc. — A  voltaic  arc  whose  electric  power  is  reck- 
oned in  watts. 

Watt-Hour. — A  unit  of  electric  energy  or  work.  One 
watt  exerted  or  expended  for  one  hour. 

Wattmeter. — An  instrument  serving  to  measure  the 
power  of  a  circuit. 

Wave  Winding. — A  winding  which  resembles  a  wave 
in  form.  Continuous  or  undulatory  winding. 

Weber. — The  practical  unit  of  magnetic  flux.  A  name 
suggested  by  Clausius  and  Siemens  to  denote  a 


310  ELECTRICAL  DICTIONARY 

magnet  pole  of  unit  strength;  but  the  use  of  the 
term  has  been  abandoned. 

Weber's  Theory  of  Diamagnetism. — A  theory  which  as- 
sumes originally  magnetized  atoms  in  order  to 
account  for  diamagnetism. 

Weight  Efficiency  of  Transformer.— A  transformer's 
specific  activity. 

Welding. — Uniting  metals  at  a  high  temperature  and 
leaving  no  trace  of  a  junction. 

Welding  Converter. — A  transformer  used  to  step  down 
an  alternating  current  which  is  used  for  the  pur- 
pose of  fusing  or  welding  metals  together. 

Welding,  Electric. — Welding  by  the  use  of  heat  electri- 
cally generated. 

Welding  Transformer. — A  step-down  transformer  used 

in  electric  welding. 
Welsbach  Burner. — A  mantle  covered  with  refractory 

material  whose  light  is  due  toancandescence  under 

the  action  of  a  Bunsen  flame. 

Western  Union  Splice. — An  American  wire  joint. 
Wheatstone's  Electric  Balance. — An  electric  bridge  or 
balance. 

Wheatstone's  Bridge. — A  Wheatstone's  electric  bal- 
ance. 

Whistling  Effect. — In  a  carbon  transmitter  and  tele- 
phone receiver  in  a  line,  an  effect  produced  when 
the  transmitter,  being  close  to  the  receiver  is 
slightly  jarred,  resulting  in  the  emission  of  a  musi- 
cal sound  by  the  receiver  and  which  reacts  upon 
the  transmitter,  producing  similar  sounds  in  other 
receivers  on  the  same  circuit. 


ELECTRICAL  DICTIONARY  311 

White  Heat. — That  temperature  of  a  heated  body  at 
which  it  glows  with  a  white  heat. 

Wind,  Electric. — A  rush  of  air  atoms  from  a  point  con- 
nected to  a  condenser  statically  charged. 

Windings. — The  coils  put  on  the  armature  of  a  dynamo 
or  motor  or  on  an  electro-magnet's  core. 

Wipe  Spark. — A  spark  emitted  from  a  spark  coil  pro- 
duced by  the  wiping  contact  of  a  spring. 

Wiped  Joint. — A  plumber's  joint.  A  joint  formed  in 
the  lead  sheathing  of  a  cable  by  applying  free 
metal  to  the  surfaces  as  done  by  plumbers. 

Wiping  Contact. — The  contact  made  by  one  conductor 

wiping  against  another. 
Wire  Splice. — A  splice  made  between  two  lengths  of 

wire. 

Wire  Terminals. — Eyes  of  metal  suitable  to  solder  to 
the  ends  of  wires  for  switchboard  connections. 

Wire-Wound  Armature. — -An  armature  whose  windings 
consist  of  wire  in  distinction  to  one  wound  with 
bars. 

Wireless  Telegraphy. — A  term  meaning  any  system  of 
telegraphic  communication  which  can  be  carried 
on  without  circuits  composed  of  wires. 

Wiring. — Placing  wires  in  a  circuit.  All  of  the  electric 
conductors  employed  in  an  electric  distribution  cir- 
cuit referred  to  collectively. 

Work. — The  action  of  a  force  through  space  against 
resistance. 

Woven-Wire  Dynamo  or  Motor  Brushes. — Brushes 
made  of  gauze  for  dynamos  or  motors. 


312  ELECTRICAL  DICTIONARY 


X-Ray  Lamp. — A  high  vacuum  tube  lamp  whose  in- 
terior walls  are  covered  with  crystals  of  calcium 
or  other  fluorescent  substances  and  which  when 
exposed  to  X-Rays  gives  out  light. 

X-Ray  Photograph. — A  term  signifying  radiograph. 

X-Ray  Transformer. — A  transformer  serving  to  obtain 
the  high  potential  discharges  used  in  X-ray  tubes. 

X-Rays. — A  curious  kind  of  radiation  discovered  by 
and  named  after  Roentgen,  the  exact  nature  of 
which  is  not  yet  known.  Rays  which  readily  pene- 
trate and  pass  through  divers  substances;  causing 
fluorescence  in  certain  bodies  and  producing  on 
photographic  plates  an  actinic  effect;  causing  the 
discharge  of  an  insulated  charged  conductor,  and 
producing  a  troublesome  affection  of  the  skin  when 
exposed  to  the  rays  too  long. 


Y. 

Y-Connection  of  Three-Phaser.— Star  connection.  The 
connection  of  a  triphaser's  three  circuits  to  the 
.same  junction,  and  resembling  the  letter  Y  in  ap- 
pearance. 

Y-Connected  Three-Phaser  Armature. — A  triphase  arm- 
ature with  three  circuits  connected  in  common  to 
one  point. 

Y-Current. — A  current  in  a  triphase  system  between 

any  wire  and  the  neutral  point. 
Y-Potential  of  Triphase  System. — In  a  triphase  system, 

the  effective  difference  of  potential  or  voltmeter 


ELECTRICAL  DICTIONARY  313 

pressure  between  one  terminal  or  conductor  and 
the  neutral  point. 

Yoke. — The  piece  of  iron  in  an  electro-magnet  which 
connects  the  ends  most  remote  from  the  poles  of 
the  two  parts  of  the  core  where  the  wire  has  been 
wound. 

Z. 

Zinc-Battery. — A  battery  which  decomposes  zinc  in  an 
electrolyte,  thereby  producing  a  current. 

Zinc-Carbon  Voltaic  Cell. — A  voltaic  cell  consisting  of 
a  suitable  electrolyte  into  which  is  immersed  a 
zinc-carbon  couple. 

Zinc  Currents. — Negative  currents. 

Zinc-Lead  Accumulator. — A  secondary  cell  in  which 
are  used  lead  and  zinc  plates. 

Zinc  Plating. — The  employment  of  zinc  in  electro-plat- 
ing. 


Books  That  Really  Teach 

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